PRSS Glossary:
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16 (points) Quadrature Amplitude Modulation (16-QAM):
A sophisticated modulation technique, or compression technique, using variations in signal amplitude and phase that allows multiple bits to form a single “symbol,” which then is impressed on a single sine wave. “Quadrature” refers to the fact that four (i.e., “quad”) distinct amplitude levels are defined.16 QAM creates a symbol of four bits through 16 distinct signal points, or variations in amplitude and phase. See also: quadrature amplitude modulation
8 Phase Shift Keying (8PSK):
Used by relatively sophisticated modems for transmitting digital signals over a carrier. In phase shift keying, the phase of the carrier signal is changed to reflect a change in value of the adjacent bits. The receiving device looks for the phase shift of the signal in absolute, rather than relative, terms. See also: phase shift keying
A La Carte Services :
Separate pricing is offered for each web service component.
A Real-Time Interface Coprocessor (ARTIC):
The adapter board, which resides in the IBM-compatible computers at uplinks, downlinks, and the STC. The ARTIC card controls communications with the equipment that is used by the SOSS software: demodulators, modulators, tape recorders, DACS advisory panels, ESN key, and other devices for control and/or status from connected devices. The ARTIC card enables the SOSS computer to send and receive multiple signals simultaneously. See also: ARA, DACS, SOSS
ABR-700 :
The model of ComStream digital audio demodulator employed by the PRSS. See also: audio demod, demodulator
Acknowledgment (ACK):
In data communications, ACK is a character transmitted by the receiver of data to acknowledge a signal, information, or packet received from the sender. The transmission of ACK characters from the receiving device to the sending device indicates the data sent has been received correctly.
Actor :
A term used in the rational unified process to denote someone or something that interacts with the system (or business) See also: Rational Unified Process
Alternate Feed :
An extra feed of a program, scheduled on Distribution’s own initiative, in addition to the primary feed. Alternate feeds are mostly scheduled due to sun outage interference, but may be scheduled for other reasons as well. See also: makegood, prefeed, refeed, repeat, retransmission
American National Standards Institute (ANSI):
Membership organization that coordinates the development of U.S. voluntary national standards for both the private and public sectors.
Amplitude Modulation (AM):
A form of modulation where the amplitude, or level of the carrier, is modulated by the baseband signal.
Analog :
A mode of audio recording or transmission whereby the electrical signal is “analogous to” or resembles its physical properties, for example a louder passage having a higher voltage.
Antenna :
Used for receiving RF signals. The classic broadcast satellite antenna is a parabolic reflector. Sometimes called a “dish” due to its shape.
Application Program Interface (API):
A set of programming functions within an application or operating system that define how a specific service can be invoked from software.
Application Server :
Software in an intranet/Internet environment that hosts a variety of language systems used to program database queries and/or general business processing.
Arc Diagram :
A computer-generated depiction of the positions of the domestic satellites as they would be seen from a potential earth terminal location.
ARTIC Breakout Box :
A parallel signal splitter that provides up to eight distinct serial buses to and from the ARTIC card. Each RJ-11 jack services one bus. See also: ARTIC
Artifact :
A piece of information that 1) is produced, modified, or used by a process, 2) defines an area of responsibility, and 3) is subject to version control. An artifact can be a model, a model element, or a document. See also: Rational Unified Process
Asserted :
The state of a GPI status input when it is considered to be active. In the SOSS setup program, status inputs can be deemed “asserted” due to the presence or absence of voltage. See also: GPI, SOSS
Asymmetrical Digital Subscriber Line (ADSL):
A high-speed data transmission technology. ADSL (a) uses existing unshielded, twisted-pair copper wires from the telephone company central office to the subscriber’s premises; (b) involves electronic equipment in the form of ADSL modems at both the central office and the subscriber’s premises; (c) sends high-speed digital signals up and down those copper wires, and; (d) sends more information one way than the other.
Asynchronous Transfer Mode (ATM):
A fast, cell-switched technology based on a fixed-length 53-byte cell. All broadband transmissions (whether audio, data, imaging, or video) are divided into a series of cells and routed across an ATM network consisting of links connected by ATM switches. Each ATM link comprises a constant stream of ATM cell slots into which transmissions are placed or left idle if unused.
Audio Demod :
The ABR-700 demodulators that are tuned to receive Intermediate Frequencies (IF) containing audio transmissions. They demodulate the IF signal and pass the audio signal to station audio equipment. See also: demodulator, IF
Audio Frequency :
The band of frequencies that can be heard by the human ear, generally between 20–20,000 Hertz. See also: baseband, Hertz, IF, RF
Audio Recording Automation (ARA):
The subsystem of the SOSS that allows downlinks to capture programming off the satellite in an automated fashion. The system consists of an IBM-compatible computer using the OS/2 operating system, an ARTIC coprocessor card, and several GPI boxes. ARA controls demodulators, tape recorders and other audio storage devices, audio routing switchers, and other station equipment over a serial control line. ARA also has the capability of acting as an automation system for the station’s on-air signal. It continuously monitors the DSC and stores updates to the system schedule. It continuously executes the events defined for transmissions in the local station schedule by sending control commands to connected station resources. The ARA may be monitored and controlled by using the operator action display application. See also: ARTIC, DSC, GPI, operator action display, SOSS
Authorization File :
A file sent to the ContentDepot delivery system, indicating which stations are entitled to receive producer content. See also: ContentDepot
Authorized Requestor :
A person authorized by a registered source to request time on the satellite schedule. See also: registered source
Auto-On, Auto-Off mode :
Automation on or off. In the ARA software, the state in which automatic execution of transmissions is either enabled or disabled. See also: ARA
Automatic Gain Control (AGC):
The circuit available on most demodulators that allows the demod to successfully receive signals of widely varying levels. A voltage produced by this circuit, called the AGC voltage, is roughly proportional to the received signal level. Therefore, it may be used as an aid in peaking a satellite antenna once the correct signal has been found.
Automation Interface :
In the ContentDepot delivery system, the automation interface allows the station automation system to communicate with the station controller, which informs the station platform of where and when to route audio.
Automation System :
In the ContentDepot, the term automation system is a generic term for any computer-based system that stores and plays audio files. In many cases, the system provides true automated functions: playout at future times, repeating schedules, file sequencing, and external controls (like operating audio routing switchers and broadcast consoles).
Available Bit Rate (ABR):
An ATM level of service that adjusts bandwidth according to congestion levels in the network. It does not guarantee a specific amount of bandwidth, and the end station must retransmit any information that did not reach the far end. See also: ATM
Azimuth :
Compass bearing (measured from true north rather than magnetic north) that describes the direction a satellite antenna must point to acquire a particular satellite. See also: antenna, declination, elevation
Back Channel :
See also: Internet back channel
Back-up Site :
A second site for hosting the PRSS ContentDepot. See also: ContentDepot
Backhaul :
A point-to-point feed from a remote location to a station or uplink (via satellite, land-line, microwave, or fiber-optic link) for program production or transmission to stations. See also: fiber optic, first mile, ISDN, microwave, telephone line
Bandwidth (BW):
A section of the electromagnetic spectrum between two frequencies. Each carrier on the satellite system has, in addition to a center frequency, a specific bandwidth that determines the carrier’s ability to carry complex or detailed signals. The broader the bandwidth of a satellite channel, the better quality audio it can carry. “Narrowband” channels can only carry voice-grade audio while “wideband” channels can carry high-quality audio. The radio frequency bandwidth of a channel is larger than the bandwidth of the audio it can carry. Satellite channels may sometimes be referred to by their audio bandwidth and sometimes by their radio frequency bandwidth. See also: frequency, power
Barter Trading :
Services provided without the exchange of money.
Baseband :
Pertaining to a signal in its original form, not changed by modulation. The baseband signal in public radio satellite transmissions is audio; the satellite RF carrier is downconverted to IF, which is then demodulated into audio. In a digital demodulator, this audio is a digital signal that is further decoded into program audio. See also: audio frequency, IF, RF
Basic Rate Interface (BRI):
In ISDN, the subscriber interface consisting of two bearer B-channels at 64 kilobits per second and a data-D channel at 16 kilobits per second. The bearer B-channels are designed for Pulse Code Modulated voice, slow-scan video conferencing, Group Four facsimile machines, or whatever you can squeeze into 64,000 bits per second full duplex. The data (or D) channel is for bringing in information about incoming calls and taking out information about outgoing calls. It is also for access to slow-speed data networks, such as videotex, packet switched networks, etc. See also: ISDN, PRI
Baud Rate :
A measure of how frequently sound changes on an analog phone line when used for data transfer. In this mode, digital signals are converted by a modem into analog audio tones, which can be sent over a standard telephone line. The baud rate is a unit of modulation rate. One baud corresponds to a rate of one unit interval per second, where the modulation rate is expressed as the reciprocal of the duration in seconds of the shortest unit interval. Note: Baud is sometimes used as a synonym for bit-per-second (bps), which is incorrect.
Binary Digit (bit):
A bit (short for binary digit) is the smallest unit of data in a computer. A bit has a single binary value, either 0 or 1.
Binary Phase Shift Keying (BPSK):
A method of phase-modulating a radio frequency carrier with digital information in which the instantaneous phase angle of the received carrier determines whether a zero or a one is being received. The two possible phase angles are 180 degrees apart. See also: QPSK
Bit Error Rate (BER):
The percentage of received bits in error compared to the total number of bits received.
Bit Rate :
The transmission speed of a data signal. Different than baud rate, which is the frequency of the audio encoding signal used when data is transmitted over long distances by modem. The public radio modulators and demodulators can use any of several available bit rates, using more bandwidth and yielding better quality audio or more channels as the bit rate increases. See also: bandwidth, baud rate, frequency
Bits Per Second (bps):
The number of bits passing a specific point per second. See also: bit rate
Block Feed :
An arrangement whereby several audio programs are transmitted together as a single feed with one start time and one end time for the group, but not for individual programs within the group.
Border Gateway Protocol (BGP):
A gateway protocol which routers (other non-router devices also may be involved as intermediaries) employ in order to exchange appropriate levels of routing information. See also: gateway protocol
Breakout Box :
See also: ARTIC breakout box
C-band :
In satellite communications, C-band generally denotes any system, satellite, or earth station that uses frequencies between 5925 and 6425 MHz for uplink and those between 3700 and 4200 MHz for downlink. The PRSS is a C-band communications system. See also: Ku-band
Carriage Report :
A report that itemizes the confirmed airing of programs as reported by the station, producer, or other research entities. See also: usage report
Carrier (CXR):
A radio frequency wave that can be sent long distances by transmitting it from an antenna. When modulated by an audio, video, or data signal, a carrier becomes a useful tool for communications. Carriers are designed so that they fit into individual channels on a satellite or transponder.
Cascading :
Putting an audio signal through a digital encoding/decoding process more than once, possibly using more than one coding scheme. Signal degradation may occur as a result of too many passes through the encode/decode process.
CD Quality :
A buzzword implying that the digital transmission (or storage and retrieval) system being described is mostly indistinguishable from the playback quality of a compact disc (44.1 kHz sampling rate, 16 bit, stereo linear encoding). The lossy coding algorithms that must be used to make satellite transmission feasible cannot, by design, sound exactly like a digitally mastered compact disc. “Near CD-quality” more accurately describes the audio received by the PRSS digital demodulators. See also: compact disc
Central Platform :
The portion of the ContentDepot delivery system that is located at a hub. See also: ContentDepot
Central Platform Controller :
A software device that coordinates and commands other devices for initiating functions within the ContentDepot delivery system such as receive, record, store, play, and decode. The controller receives its instructions from the ingest and delivery schedule and any time-critical messaging. See also: ContentDepot
Change Request (CR):
In the rational unified process, changes to development artifacts are proposed through change requests. Change requests are used to document and track defects, enhancement requests, and any other type of request for a change to the product. The benefit of change requests is they provide a record of decisions and, due to their assessment process, ensure that the impact of changes is understood across the project. See also: Rational Unified Process
Channel :
A part of a satellite transponder capable of carrying a single audio, video, or data signal. A transponder may be used as a single channel or divided into as many as hundreds of channels.
Channel Format :
A set of technical specifications assigned to a satellite channel that determines its power, bandwidth, pre-emphasis, audio bandwidth, bit rate, noise reduction, and other factors. For a satellite channel to work in proper broadcast quality, the format of the demodulator used to receive it must be identical to the format of the modulator used to originate it. In the single-channel-per-carrier satellite audio distribution industry, there is not one standard channel format.
Class(es) :
A description of a set of objects that share the same responsibilities, relationships, operations, attributes, and semantics.
Closed Circuit :
Also called an “interconnect.” A feed that is transmitted to stations, but is not intended for over-the-air broadcast. Closed circuit feeds are often used as a means of informing stations about new programs or membership or interconnection issues, and are sometimes produced as a teleconference so station staff can listen to the satellite feed and call the NPR studio with comments.
Co-location Web Hosting :
Relocating equipment owned by the station to the hosting provider's own facility. The hosting provider provides the power, on-ramp to the Internet, and some level of maintenance.
Coder-Decoder (CODEC):
A general term applied to encoders and decoders, as they are usually used in a complementary fashion.
Commercial-Off-The-Shelf (COTS):
A standard, widely available product that is suitable for the intended use without modification. Typically used to refer to computer software, in contrast to “custom” software, which was developed for a specific customer’s needs instead of the general market.
Common Carrier :
A government-regulated private company that offers telecommunications services or communications facilities to the general public on a non-discriminatory basis. Common carriers are required by the regulating governmental agency to file a tariff, schedule of charges, and terms and conditions that act as a contract between the subscriber and the carrier. Telephone companies are examples of common carriers.
Compact Disc (CD):
A form of audio media storage where the sound is converted to a digital format and then stored in the form of microscopic “pits” representing the digital signal on metallic film encased in plastic. The pits are then read by a laser system as it scans the disc.
Compander :
A compressor-expander system used to compress the dynamic range of an analog signal before transmission and expand it after reception in order to improve the signal-to-noise ratio. See also: compression
Component :
A component is a nontrivial, nearly independent, and replaceable part of a system that fulfills a clear function in the context of a well-defined system architecture. See also: Rational Unified Process
Compression :
In analog transmission, the act of squeezing the loudness of an audio signal so that it can be transmitted through a communications channel that is otherwise too noisy to carry it. In digital transmission, the reduction of bit rate of a digital signal. See also: channel format, compander, data reduction, dbx, Dolby, MUSICAM
Computer (CPU):
A programmable electronic device that can store, retrieve, and process data.
Comrex® :
A means of altering the frequencies of an audio signal so that better low-end (bass tones) can pass through a dial-up telephone line. At the receive end, a second Comrex device restores the original frequencies. Comrex is used when higher-quality means of transmission (such as ISDN) are not available. It prevents telephone voice quality from sounding “thin.” A second version of Comrex uses two dial-up telephone calls to transmit even better quality audio. Sometimes used as a first mile to a satellite uplink. See also: first mile, ISDN
Configuration :
A configuration is the set of system artifacts that define a particular version of a system or part of a system. See also: Rational Unified Process
Confirmed :
When NPR Distribution and the customer have agreed on a program’s placement in the schedule, that space has been reserved accordingly, and the uplink has been notified, the program is said to be “confirmed.” See also: unconfirmed discount
Consultative Committee on International Telephone & Telegraph (CCITT):
The CCITT, now known as the ITU-T (Telecommunication Standardization Sector of the International Telecommunications Union), is the primary international body for fostering cooperative standards for telecommunications equipment and systems. It is located in Geneva, Switzerland. See also: International Telecommunications Union
Contact Closure :
The switching or signaling that allows enabled equipment to automatically respond and perform specific actions based upon that signaling. In band or out of band (in channel or out of channel), coding, or electrical signaling is used to instruct the equipment to respond to these commands or signaling.
Content :
Radio programs and web objects stored and transmitted in the ContentDepot delivery system. See also: ContentDepot
Content Essence :
Refers to the actual audio program without any metadata. See also: metadata
Content Exchange :
A service of the ContentDepot, a content exchange is an online community where members of a broadcast community can place and retrieve content for on-air or other uses. See also: ContentDepot
Content File :
A file in the central platform of the ContentDepot delivery system that serves as a repository of radio program and other content. See also: central platform
Content Management :
The methodology for handling the content within the ContentDepot. See also: content, ContentDepot, content essence, digital asset management
Content Metadata :
Text related to the content of a program. It contains items such as rundowns, text cues, rights, etc.
ContentDepot :
The next generation PRSS distribution system that will provide program delivery and services to public radio producers and stations.
ContentDepot Catalog :
Provides a centralized location to find programs, program information, and other related elements. The Catalog facilitates a powerful exchange of public radio program assets and information between program producers/distributors and stations. See also: ContentDepot
ContentDepot Hub :
The facility that houses the information system and the delivery system. There are two hubs. See also: ContentDepot
ContentDepot Portal Interface :
A website through which ContentDepot services are provided. Users will be able to manage subscriptions, user profiles, and directories and search and audition programs, as well as upload actual content. See also: ContentDepot, portal
ContentDepot Reference Architecture :
An example design intended to illustrate one way the ContentDepot delivery system can be built. See also: ContentDepot
ContentDepot Satellite Transmission (ContentDepot Satellite Transmission ):
Represents each specific content delivery from the ContentDepot central platform, regardless of type. Currently, there are three types of content delivery: live program, stored program, and content exchange. These are represented in the station platform as transmission streams (for live programs) and stored transmissions (for stored programs and content exchanges). The key difference between stored programs and content exchanges is that stored program transmissions are scheduled, and content exchanges are on demand. See also: central platform, ContentDepot, content exchange, live program, stored program
ContentDepot Schedule :
The master schedule for the ContentDepot head-end that determines the entire offering of programs available to stations for live and stored programs. See also: ContentDepot, delivery schedule
Contributing Station :
An interconnected public radio station that pays a reduced D/I fee while giving up some benefits of participating station status. See also: interconnected station, participating station
Control Outputs :
Any pair of GPI terminals labeled “control output” that receives commands from the SOSS computer that are intended for a connected device (such as a tape deck). Control outputs can be used to simulate any push-button or other control of a device. See also: General Purpose Interface, SOSS, status inputs
Cue, also Cueing :
A special type of messaging, created by a producer and consisting of metadata, that informs stations of system actions that are necessary for the proper presentation of the program. These system actions are time critical or non-time critical. Some cueing is synchronous with the content essence. See also: content essence, metadata
Custom Web Hosting :
Web hosting customized by the hosting provider to meet the individual requirements of the station's current web service needs. See also: web hosting
Customer Service Unit/Data Service Unit (CSU/ DSU):
A piece of equipment that is used as an interface between a digital telephone circuit and the CODEC. This equipment coordinates timing and protocols between the phone line and the CODEC. See also: CODEC, ISDN, terminal adapter
Cyclic Redundancy Check (CRC):
A process used to check the integrity of a block of data. A CRC character is generated at the transmission end. Its value depends on the hexadecimal value of the number of ones in the data block. The transmitting device calculates the value and appends it to the data block. The receiving end makes a similar calculation and compares its results with the added character. If there is a difference, the recipient requests retransmission. CRC is a common method of establishing that data was correctly received in data communications.
DACS Advisory Panel :
Hardware that displays a notification that an incoming DACS message is urgent or very important. Can be configured to activate external alarms. See also: DACS
DACS Attachment or Attached File :
A file that you can send along with a DACS message, such as a document, a compressed set of files, or an executable file. See also: DACS
DACS Capture :
Custom software application in the SOSS that continuously monitors the DSC for incoming DACS messages, transmission schedules, and time synchronization. DACS capture should operate around the clock, and receives only those transmissions addressed for a particular station. See also: DACS, DSC, SOSS
DACS View :
Custom software application used to view and manage DACS messages. See also: DACS
Data Backup and Recovery :
A combination of manual and automated procedures that can restore lost data in the event of hardware or software failure. Routine backup of databases and computer activity logs are part of a backup and recovery program.
Data Channel :
A subset of bandwidth on the MCPC satellite uplink used for sending messages, graphics and web modules, and radio program files requested from the content file. See also: content file, MCPC
Data Model :
The data model describes the logical and physical representation of persistent data in the system. It also includes any behavior defined in the database, such as stored procedures, triggers, and constraints. See also: Rational Unified Process
Data Reduction :
Using an algorithm to greatly reduce the number of bits per second. Some audio information is discarded and not recovered upon decoding.
Database (DB):
A large collection of data organized for rapid search and retrieval.
dbx® :
A proprietary process of audio compression used to reduce the audible hiss and other noise on recordings. A tape recorded with dbx encoding requires special equipment to decode the audio before it can be used. See also: compression, Dolby
DC Update :
A DACS message sent in the afternoon each business day highlighting last-minute changes to the satellite schedule for the next day or for the weekend. See also: operations schedule
Dead Letter Queue :
Unaddressed messages sent to the station platform are placed in the dead letter queue within the ContentDepot delivery system for later processing or deletion. See also: station platform
Decibel (dB):
A unit of measurement that indicates the difference in level between two audio sources. The dB scale is logarithmic in order to match the mechanics of human hearing and can only be used to show a fixed loudness or signal level when referenced against a known standard such as one milliwatt into 600 ohms (dBm), one watt (dBW), one volt (dBv), etc. Thus, an audio signal may never be said to be 3 dB in level, although it can be 3 dB higher in level than another signal (indicating the difference between the two), and it can be +3dBm (indicating the difference between it and 1 milliwatt at 600 ohms). Because of the logarithmic scale, doubling the signal level (an increase of 3 dB, such as from 2 watts to 4 watts) does not double the loudness to the ear; rather, it produces a change in loudness that is barely noticeable. A perceived doubling of sound level requires an increase in the signal level of 10 dB.
Declination :
The angle between magnetic north and true north; declination must be added to or subtracted from the magnetic compass reading to obtain a true bearing or azimuth. See also: azimuth
Decode :
A digital signal that is processed through either hardware or software to become analog audio that can be routed, recorded, played out, or stored at the station platform. See also: station platform
Decoder :
A device that translates a digital audio bitstream back into analog audio. See also: encoder
Dedicated Web Hosting :
In this scenario, the station has exclusive use of the server leased by the hosting provider.
Delivery Schedule :
A table maintained in the central platform that indicates which radio programs will be broadcast from the STC, and the time and duration of the program broadcast. This is the master schedule for the ContentDepot that determines the entire offering of programs available to the stations for live and stored programs. See also: central platform, ContentDepot, ContentDepot schedule
Delivery Schedule Update Notification :
A broadcast message indicating a change in the delivery schedule. See also: delivery schedule
Demand Assigned Multiple Access (DAMA):
A way of sharing a channel’s capacity by assigning capacity on demand to an idle channel or an unused time slot.
Demodulator (DEMOD):
A piece of equipment used by a satellite downlink to receive an individual audio or data channel. The demodulator receives one modulated carrier signal from a transponder and strips out the carrier signal, leaving an audio or data signal usable by the party receiving it. Some demods, called “fixed” or “fixed-tuned” demods, can receive only one channel. Other demods, called “fully-agile” demods, can receive all of the channels on a transponder (one channel at a time). A separate demodulator is required for each channel that must be received simultaneously. There is no limit on the number of demodulators that may exist at a downlink. See also: bandwidth, carrier, channel format, deviation, frequency, integrated receiver/decoder, modulation, modulator
Demodulator Authorization (DA):
A system of data and data transport that allows a Comstream ABR700 demodulator to unmute its audio outputs only if a specific authorization code is embedded in the received signal. This authorization system is used to limit satellite reception of certain radio programs to specific subscriber stations. Also abbreviated as “demod authorization.”
Deviation :
A measurement of modulation that an audio, video, or data signal impresses upon a carrier when using frequency modulation. See also: bandwidth, carrier, channel format, demodulator, frequency, modulation, modulator
Dial-up :
An inexpensive method of sending audio from one city to another. A long distance telephone call is established between the two cities and the audio program is sent over the phone. Often used to back up a failure in a satellite transmission. A dial-up may be analog (POTS–Plain Old Telephone Service) or digital (ISDN). See also: ISDN, POTS
Digital :
A mode of recording or transmission whereby the audio is “described” by an electrical signal consisting of a series of ones and zeroes, or binary digits. A change in the physical properties of the audio, such as an increase in volume, has no effect on the physical properties of the electrical signal, other than a different sequence of ones and zeroes. See also: analog
Digital Asset Management (DAM):
Methodology for maintaining and managing a repository for any or all digital content and media. Short descriptions or thumbnails of digital content, known as metadata, are stored in a database for easy searching and management. DAM can also refer to the procedures for facilitating the management of intellectual property or copyrighted content.
Digital Audio Tape (DAT or RDAT):
A tape-based digital system for recording and playing audio programs. DAT tapes are often used to provide programs to uplinks for satellite transmission and for recording programs off the satellite.
Digital Audio Workstation (DAW):
A computer with software capable of recording, editing, playing back, and otherwise manipulating audio. It is possible to produce entire radio programs on a DAW.
Digital Broadcasting System (DBS):
When used within the PRSS context, the term refers to the recording, storage, and distribution of digitally encoded audio files. Outside of PRSS, this term may also be used to refer to direct broadcast satellite.
Digital Signal Processor (DSP):
A specialized microprocessor chip designed to digitally process signals. Each modulator and demodulator in the digital audio transmission system contains a DSP running a program that is the MUSICAM coding or decoding algorithm. See also: decoder, encoder, musicam
Digital Signal, Level (X) (DS-X (X=0-4)):
A designator for a digital channel. DS-0 is 64 kbps. DS-1 is 1.544 Mbps (also known as a T-1). DS-2 is 6.312 Mbps. DS-3 is 45 Mbps. DS-4 is 274.176 Mbps.
Digital Subscriber Line (DSL):
A modem technology that uses existing twisted-pair telephone lines to transport high-bandwidth data, such as multimedia and video, to service subscribers. Also called xDSL. The term xDSL covers a number of similar yet competing forms of DSL, including ADSL, SDSL, HDSL, RADSL, and VDSL. It delivers high-bandwidth data rates to dispersed locations with relatively small changes to the existing telco infrastructure. DSL lines typically operate on one pair of wires like a normal analog phone line. See also: ADSL
Digital Video Broadcasting (DVB):
A set of standards that define digital broadcasting using existing satellite, cable, and terrestrial infrastructures. DVB is an open system as opposed to a closed system.
Direct Access Communications System (DACS):
A system in the SOSS for electronic message delivery to public radio stations. DACS messages are carried by satellite simultaneously to all addressed stations. DACS messages may be sent by registered sources of programming, public radio stations or other public broadcasting entities, and NPR staff. See also: SOSS, WebDACS
Direct Control Program (DCP):
Custom software application that enables you to remotely control and monitor any resource in real time. This program can be used to send control commands to ARA resources independently of the local station schedule. The DCP shows the operating status of each resource. See also: ARA
Directory :
A table indicating which content is available in the ContentDepot content file. See also: ContentDepot, content file
Discipline :
A discipline is a collection of activities that are related to a major “area of concern” within the overall project. See also: Rational Unified Process
Dish :
Slang for a satellite antenna.
Distribution :
The process of delivering programming to public radio stations. Distribution was formerly accomplished by a combination of a nationwide telephone network accompanied by tape duplication and mailing. Since 1979 the majority of public radio distribution has been by satellite. Also, Distribution is the corporate division of NPR that manages this amazing feat. See also: antenna
Distribution Agreement (D/I Agreement):
A contract between a program supplier and NPR Distribution. Along with an initial registration fee, this allows the supplier to distribute programming on the PRSS. By signing the agreement, the program supplier accepts full legal responsibility for the programs they distribute, indemnifies NPR and any interconnected stations which air any of the programs, and accepts responsibility for obtaining liability insurance as well as rights and clearances as necessary.
Distribution Information Services (DIS):
The group within NPR Distribution who provide computer services to the Division, and, by extension, its customers.
Distribution/Interconnection Committee (D/I Committee):
The committee of the NPR Board of Directors responsible for recommending rates and policy and for overseeing the operations of the PRSS.
Distribution/Interconnection Fee (D/I Fee):
An annual fee paid by satellite-equipped public radio stations as their share of the cost of operating and maintaining the satellite system. See also: interconnected station, satellite interconnection agreement
Dolby® :
A proprietary process used to reduce the audible hiss on recordings and FM broadcasts. The letter that sometimes follows the word “Dolby” indicates the specific version of this process, such as “Dolby-A” or “Dolby-B.” A tape recorded with Dolby processing requires special equipment to decode the audio before it can be used. See also: compression, dbx
Domain Name System (DNS):
Name resolution software that allows users to locate computers on a UNIX network or the Internet (TCP/IP network) by domain name. The DNS server maintains a database of domain names (host names) and their corresponding IP addresses.
Double Hop :
A method of getting a program from an uplink to a downlink by using two satellite links instead of one. This may be done in cases where the uplink and the downlink are pointed at different satellites and cannot be repointed to the same satellite for this feed. It can also be used when the channel format transmitted by the uplink is not compatible with the demodulators at the downlink. The double hop is accomplished by establishing an uplink/downlink which is capable of receding both satellite links or dealing with both signal formats at once. This site, known as the turnaround site, receives the signal from the first satellite link and then re-transmits it to the second satellite link. The amount of satellite delay in a double hop is about a half-second, twice as much as for a single hop. If a station is doing two-way conversations between its studio and the satellite remote site, this double-hop delay can be annoying and confusing. See also: hop, satellite delay
Double Illumination (DI):
A condition where two or more carriers are on the same frequency at the same time. The carriers may be from the same or different uplinks. The audible effect of double illumination can range from almost no audible change to complete impairment depending on carrier power and other factors. See also: carrier
Downconverter :
A device used in a satellite receiving system that converts the output of the dish antenna’s LNA or LNB to a frequency range that can be received by the satellite demodulator.
Downlink (D/L):
A satellite earth terminal capable of receiving signals from the satellite. Every interconnected station in the PRSS has a downlink. Some also have uplinks. See also: uplink
Downlink Services Channel (DSC):
The satellite data channel used by the SOSS for delivering DACS messages, and scheduling records, time synchronization signals, and other control information to uplinks and downlinks. See also: DACS, SOSS
Dropout :
A defect on a tape-recording that causes the audio to drop in level or disappear altogether momentarily. Dropouts are frequently caused by manufacturing defects, poorly assembled splices, poor tape handling that damages the tape, or mistracking of digital tapes.
DSC Demod :
The ABR-700 demodulator that is dedicated to receiving the DSC and routing DSC data to the SOSS computer for further processing. See also: ABR-700, DSC, SOSS
Dynamic Host Configuration Protocol (DHCP):
A TCP/IP Protocol that enables computers to get temporary or permanent IP addresses from a pool of numbers available from centrally administered servers.
Electronic Commerce (E-commerce ):
The use of computers and electronic communications in business transactions. E-commerce may include the use of electronic data interchange (EDI), electronic money exchange, Internet advertising, websites, online databases, computer networks, and point-of-sale (POS) computer systems.
Electronic Serial Number key (ESN):
A small electronic device connected to the SOSS computer that contains the unique PRSS ID for the station. A station receives DACS messages for this ID only. The SOSS computer polls the ESN key periodically to obtain and verify the ID. See also: DACS, SOSS
Elevation :
Angular measurement from the horizon to a satellite.
Emergency Override :
A mechanism for relinquishing or "overriding" the ContentDepot system in order to intervene and interrupt scheduled processes at the station platform. See also: ContentDepot, station platform
Encode :
An analog signal that is processed by hardware or software to become a digital signal for transfer over a satellite to the station platform.
Encoder :
A device that encodes audio into digits for transmission. In the case of the PRSS, the encoders use the MUSICAM scheme to reduce the amount of digital information in the signal for more efficient transmission. See also: CODEC, decoder, encode
End User :
A radio station or other entity that is the final destination of a program feed which is “handed off” to them by a public radio downlink via a last mile. See also: first mile, handoff, last mile, microwave, origination site, telephone line
Episode :
An individual occurrence or installment of a program for airing on a specific day.
Equivalent Isotropic Radiated Power (EIRP):
A measure of the power from the satellite that is directed toward a given point on the surface of the earth; used to calculate minimum antenna size and maximum LNA noise temperature.
Error Correction :
A method of recovering small amounts of data lost in the transmission of a digital signal so that the resulting information or audio is unaffected.
Essence :
See also: content essence
Event :
In the ARA system, a set of instructions that define how a transmission is processed at the station. The ARA system automatically executes the events associated with a transmission. Events can cause an action at any interconnected station resource. See also: ARA
Execute :
To carry out an event. The ARA system executes events by sending commands to equipment according to the local transmission schedule, as defined in the schedule editor. See also: ARA, event, schedule editor
Extensible Markup Language (XML):
The universal format for structured documents and data on the Internet. XML was created by a formal recommendation from the World Wide Web Consortium (W3C) and is similar to the language of today's web pages, the hypertext markup language (HTML). XML is a flexible way to create common information formats and share both the format and the data on the Internet, intranets, and elsewhere.
External Signal :
Any signal that originates outside of the ContentDepot system. See also: ContentDepot
External Signal Interface :
Allows station audio equipment to be controlled by the station platform. For example, the interface would allow the station platform to trigger GPI’s within the station itself. See also: station platform
Federal Communications Commission (FCC):
An agency created under the Communications Act of 1934 to regulate and oversee the public airwaves.
Feed Element or Feed Horn :
The part of an earth terminal antenna that directs RF energy at, or gathers RF energy from, the main reflector. The feed element is the part of the dish antenna that must be adjusted to set the LNA polarization angle correctly. See also: antenna, RF
Fiber Distributed Data Interface (ISO 9314) (FDDI):
A set of ANSI (American National Standards Institute) protocols for sending digital data over fiber optic cable. FDDI networks are token-passing networks, and support data rates of up to 100 Mbps. FDDI rings may use up to 200 km of optical fiber, or may employ twisted copper pairs for short hops, including terminal connections. FDDI generally is deployed in backbone applications, where it is used to join file servers, routers, switches, hubs, and other significant computing resources. See also: American National Standards Institute, Local Area Network
Fiber Optic :
A means of transmitting audio, video, or data signals that uses light waves as the carrier and ultra-thin fiberglass threads as the transmission medium. Fiber optic transmission has many of the advantages of satellite transmission (ability to carry multiple complex signals over long distances) with some significant differences: it cannot be interfered with, but it can be cut, since it requires a continuous cable, much like transmission over regular telephone lines. Unlike satellite transmission, there is no significant delay in sending a signal by fiber optics over long distances. This is because the distances involved in terrestrial transmission are short compared to the distances involved in satellite communications. See also: backhaul, satellite delay, terrestrial
File Transfer Protocol (FTP):
A protocol that allows the direct transfer of static files (ASCII text files or binary files such as sound files created in a DAW) from one networked system to another using the Internet. Files are made available for transfer by the administration of an FTP server. Individual users are able to interact with the FTP server by uploading or downloading files to or from the FTP server by using an “FTP Client” on their local networked PC. The client authenticates or logs the user into the FTP server by using either the IP address of the server or the server’s registered domain name. Once logged in to the FTP server, the individual files are selected for transfer, either for uploading or downloading, and the transfers are initiated by the execution of a “start transfer” command. See also: DAW
File-based Radio Program :
Radio programs transmitted as a packetized data file in the ContentDepot system. See also: ContentDepot
Firewall :
A method for keeping a network secure from unauthorized users. It can be a single router that filters out unwanted packets or may include a combination of routers and servers, each performing some type of firewall processing.
First Mile :
The terrestrial signal path from the program source to the uplink, usually by a telephone circuit. First mile is usually a consideration for live programs such as concerts and sports events where the audio originates across town or in a different city from the uplink. See also: backhaul, ISDN, last mile, telephone line, T-1
Footprint :
The geographic area where the signal from a particular satellite can be received. Also, the residual effect of a hop. See also: hop
Forward Error Correction (FEC):
A technique used by a receiver for correcting errors incurred in transmission over a communications channel without requiring retransmission of any information by the transmitter. Typically involves a convolution of the transmitter using a common algorithm and embedding sufficient redundant information in the data block to allow the receiver to correct.
Frame Relay (FR):
An access standard defined by the ITU-T. Frame relay services, as delivered by the telecommunications carriers, employ a form of packet switching analogous to a streamlined version of X.25 networks. The packets are in the forms of frames which are variable in length, with the payload being anywhere between 0 and 4,096 eight-bit bytes (octets).
Frequency (Hz):
The attribute of a satellite channel which determines its location in the transponder, measured in cycles per second, or “Hertz” (Hz). See also: audio frequency, bandwidth, channel format, IF, power, RF
Frequency Agile Receiver :
A receiver (demodulator) that may be quickly and precisely tuned to any frequency within its range. See also: demodulator, receiver
Frequency Coordination :
Part of the process of site selection. For planned receive-only earth terminals, frequency coordination assists stations in the selection of a site that is free of adverse interference from terrestrial users of the downlink frequency spectrum. It also prevents new sources of terrestrial interference from appearing during the time between prior coordination notice and registration of the terminal with the FCC.
Frequency Division Multiple Access (FDMA):
One of several technologies used to separate multiple transmissions over a finite frequency allocation. FDMA refers to the method of allocating a discrete amount of frequency bandwidth to each user to permit many simultaneous conversations. See also: Demand Assigned Multiple Access, Frequency Division Multiplex
Frequency Division Multiplex (FDM):
A technique in which the available transmission bandwidth of a circuit is divided by frequency into narrower bands, each used for a separate voice or data transmission channel. This means there can be many data paths on one circuit. The data is separated by “guard channels.” See also: Demand Assigned Multiple Access, Frequency Division Multiple Access
Frequency Modulation (FM):
A form of modulation where the frequency of the carrier is modulated by the baseband signal (audio). Most public radio stations transmit their signals using FM, which offers much better sound quality than AM. See also: amplitude modulation (AM), baseband, carrier, frequency, modulation
Gateway Protocol :
In a communications network, a network node equipped for interfacing with another network that uses different protocols. Loosely, a computer configured to perform the tasks of a gateway.
General Purpose Interface (GPI):
A piece of equipment used to convert serial data to parallel data and vice versa. In the PRSS, the GPI contains four relay contact outputs and four optically isolated status inputs.
General Resource :
Any device that can be controlled by the ARA that is not a demodulator or a storage device (such as a tape deck). For example, a telephone line, house lights, and a coffee pot can be general resources. See also: ARA, resources
Geostationary Orbit (GEO):
A “ring” around the earth 22,300 miles above the equator where satellites can be placed so their natural orbit around the earth matches the rotation speed of the earth. Satellites in this orbit appear to be stationary when viewed from the ground, greatly simplifying the design of earth stations and satellite systems.
Gigahertz (GHz):
One billion Hertz. See also: Hertz
Glossary :
The glossary defines important terms used by the project.
Graphical User Interface (GUI):
A generic name for any computer interface that substitutes graphics for characters.
Ground Segment :
Satellite equipment that is physically located on the ground, i.e., uplinks and downlinks, or the services they provide. See also: first mile, last mile, microwave, space segment, telephone line
Handoff :
A process whereby an interconnected station passes a satellite-delivered signal to another non-satellite-equipped entity in its local area. Typically, a handoff consists of a public radio station using a spare demodulator to receive a commercial feed and connecting the audio to a telephone line that delivers the audio to a commercial radio station or recording studio in the same town. See also: end user, first mile, last mile, telephone line
Header File :
One of the three possible components of a DACS message. The header file contains the destination addresses, the subject, and information about attachments. See also: DACS
Hertz (Hz):
One cycle per second. See also: frequency
Hold :
This is done in the OAD to keep a transmission active. See also: OAD
Hop :
A satellite transmission from one uplink through one satellite to one or more downlinks. See also: double hop, footprint, satellite delay
Hosting Service Provider (HSP):
Provides full service web hosting, including leasing server space, site design and programming, as well as all e-commerce facilities. See also: e-commerce, web hosting
Hub :
See also: ContentDepot hub
Hyper-Text Transport Protocol (HTTP):
The transport protocol used in transmitting hypertext documents around the Internet. See also: Hypertext
Hypertext :
Nonsequential writing made up of text blocks that can be linked by readers in multiple ways. This also refers to the software that allows the creation of and navigation through written, visual, and aural information data.
HyperText Markup Language (HTML):
A document format and presentation language used on the Internet. See also: hypertext
IF BUS Selector :
A unit which allows one of two 70 MHz IF signals to be routed to each of four demods at a downlink. The same unit may be used in reverse to send the outputs of up to four modulators to two upconverters at an uplink. See also: demodulator, IF
Impairment :
Any stream that is lost by the system during transfer to the station platform.
Inches-per-second (IPS):
A measure of tape speed in analog open reel tape recordings.
Increments :
Multiple-hour programs that have been broken into smaller programs for station convenience.
Ingest Schedule :
This schedule is maintained by the public radio account representative and details where and when content will be ingested into the ContentDepot delivery system. See also: ContentDepot
Integrated Receiver/Decoder (IRD):
A satellite receiver with a built-in decoder for unscrambling subscription channels. See also: demodulator
Integrated Services Digital Network (ISDN):
A service offered by the major telephone companies. Basic ISDN service combines two 64 kilobit per second digital circuits with a control circuit on a single pair of copper wires. See also: backhaul, switched 56, T1, telephone line
Interconnected Station :
A public radio station or other public telecommunications entity that owns or controls a distinct point of interconnection to the PRSS. Interconnected stations are required to sign a contract, called the satellite interconnection agreement, and share in the cost of operating and maintaining the PRSS by paying an annual fee known as the D/I fee. See also: contributing station, D/I fee, participating station, satellite interconnection agreement
Interface :
The interface defines a set of behaviors (a set of operations). See also: Rational Unified Process
Intermediate Frequency (IF):
A standard band of frequencies used within an uplink or downlink terminal; conveniently processes transporting signals without the large line losses and expensive equipment that would be necessary in the 6000 and 4000 MHz bands. Usually (as in public radio) a 40 MHz wide band centered at 70 MHz. See also: audio frequency, baseband, RF
International Standards Organization/ Motion Picture Experts Group (ISO/ MPEG):
A professional standards organization that specifies the protocols for certain reduced-data-rate digital audio encoding algorithms. See also: compression, data reduction, MUSICAM
International Telecommunications Union (ITU):
Based in Geneva, Switzerland, the ITU is a telecom standards-setting body. It presently consists of three major sectors that were established in 1992: the Radiocommunication Sector (ITU-R), the Telecommunication Development Sector (ITU-D), and the Telecommunication Standardization Sector (ITU-T). It includes IP voice, telematics, data, new services, systems, and networks (like ISDN). The ITU is a United Nations Agency and all UN members may also belong to the ITU, represented by their governments. See also: Consultative Committee on International Telephone & Telegraph (CCITT)
Internet Backchannel :
A network line that allows a return path from the station platform to the head-end. This allows station users to interact with the central platform. See also: central platform, station platform
Internet Protocol (IP):
Network layer protocol in the TCP/IP communications protocol suite. IP contains a network address and allows messages to be routed to a different network or subnet. It is a specific type of framing protocol that allows digital information to be packaged and transported in a way that allows easy routing of information from one computing device to another. IP “packets” can be transported over physical wires (for example, using the “Ethernet” protocol), over optical cables (for example, using the “Gigabit Ethernet” protocol), over wireless communications devices (for example, over the 802.11b protocol) or even encapsulated into other protocols (for example, encapsulated into a Digital Video Broadcast or DVB stream). Other protocols, such as TCP (Terminal Control Protocol), RTSP (Real-Time Streaming Protocol) and HTTP (Hyper-Text Transport Protocol) can be encapsulated into IP streams. See also: HTTP
Internet Service Provider (ISP):
A company that provides individuals and companies with access to the Internet and other related services such as email, Usenet access and web hosting.
Internet Station Advisory Group (NETSAG):
This group advises NPR's Online and Member & Program Services divisions primarily on current and future policies that can best strengthen the local/national partnership on the web.
Iteration :
An iteration is a distinct sequence of activities that results in a release (internal or external) of an executable product. See also: Rational Unified Process
Java :
A programming language introduced by Sun Microsystems in 1995. It is expressly designed for use in the distributed environment of the Internet. Java can be used to create complete applications that may run on a single computer or be distributed among servers and clients in a network. It can also be used to build a small application module or “applet” for use as part of a web page. Applets make it possible for a web page user to interact with the page.
Jitter :
The variation in delay for a packet transversing a network.
Kilo Bits Per Second (Kbps):
The rate of data passage (in bits) through a circuit.
KiloBytes (KB):
A unit of measurement for physical data storage on some form of storage device—hard disk, optical disk, RAM memory, etc.
Kilohertz (kHz):
One thousand Hertz (Hz, or cycles-per-second). See also: Hertz
Ku-band :
Any satellite or earth station which uses frequencies between 14,000 and 14,500 MHz for uplink and those between 11,700 and 12,200 MHz for downlink. The PRSS operates primarily on C-band, but may use Ku-band facilities as part of the transmission path. See also: C-band
L-band :
A frequency band sometimes used for interconnection between the antenna and downconverters at a downlink site. An L-band interconnection is capable of transmitting all co-polarized transponders on a satellite on a single cable (e.g., Transponders 1, 3, 5, etc.).
Last Mile :
The terrestrial signal path from the downlink to the program destination, usually by telephone line. Last mile is usually a consideration for “handoffs” where an NPR station will downlink the program and send it by telephone line to another station in town. See also: end user, first mile, handoff, microwave, telephone line
Lightweight Directory Access Protocol (LDAP):
This protocol defines a standard manner of organizing directory hierarchies (containing information about objects in a network’s directories) and a standard interface for clients to access directory services.
Live Program :
Any program that is sent from the head-end through the ContentDepot system in real-time to the station. By definition it is a stream and not a file.
Load ARTIC Tasks :
A software program that is used to configure the ARTIC card to perform the following real-time operations: polling of the ESN key; reception of the DSC; processing I/O over the serial control bus, controlling I/O to the optional station-supplied audio switcher. See also: serial control bus
Local Area Network (LAN):
A short distance data communications network (typically within a building or campus) used to link computers and peripheral devices (such as printers, CD-ROMS, modems) under some form of standard control.
Local Schedule :
A table indicating which real time radio programs a station will select and how the programs will be routed within a station. Each station maintains its own local schedule.
Log :
A list of programs that have already aired. A schedule shows things as they are intended to happen while a log shows things as they actually happened.
Lossy Data Reduction :
See also: data reduction
Low Noise Amplifier (LNA):
A device to raise the level of the received signals at the antenna for effective operation of the downconverter.
Low Noise Block Converter (LNB):
A device that raises the level of received signals at the satellite receive antenna and converts the satellite’s C-band frequencies to L-band for transmission over cable to the station’s receive equipment.
Makegood :
An extra feed of a program, scheduled by Distribution due to a technical or operational failure by the satellite system in delivering the primary feed to the stations. See also: alternate feed, prefeed, refeed, repeat, retransmission
Management Information Base (MIB):
A database of network performance information that is stored on a network agent for access by a network management system. MIB consists of a repository of characteristics and parameters managed in a network device such as an NIC (network interface card), hub, switch, or router. Each managed device knows how to respond to queries issued by network management protocols. See also: network agent
Masking Pattern Universal Subband Integrated Coding And Multiplexing (MUSICAM):
A proprietary format for encoding analog audio into a compressed digital audio bitstream. Digital audio compression technology such as MUSICAM makes it possible to transmit digital audio over satellite channels with the same or less bandwidth as analog channels.
Master Control :
The technical facility for production coordination for the NPR program divisions. Sometimes used by other distributors for special handling of complex feeds that cannot be done in the STC.
Master Schedule :
See also: transmission schedule
MCPC Receiver :
Station equipment capable of demodulating the MCPC uplink signal, and filtering and routing that subset of the resulting digital information that is addressed to the station. See also: MCPC, IRD, demodulator
MCPC Satellite Uplink :
The MCPC carrier transmitted from the central platform to the stations. See also: MCPC
Megabits per Second (Mbps):
Mbps as the speed of a telecommunications, networking, or local area networking transmission facility (i.e. something that moves information) means million bits per second. Mbps, referred to in the context of computing, means million bytes per second, which is the same as one million bytes per second. The number of bits depends on how many bits there are in a byte, which is typically eight.
Megahertz (MHz):
One million Hertz. One million cycles per second. Used to measure band and bandwidth. Also used by the computer industry to mean millions of clock cycles per second, a measure usually applied to the computer’s main microprocessor.
Message Purge Time :
The number of days that a DACS message can remain in the default DACS directory before it is automatically erased by the DACS capture program. See also: DACS, DACS capture
Metadata :
The information, or data, that accompanies a piece of digitized content, such as a video or audio clip, graphic, or script. Examples of metadata include description, subject heading, file format, author/producer, rights holder, etc.
Microwave :
A means of sending audio signals over short or long distances. Microwave transmission is technically similar to satellite transmission (both use high-frequency RF, employ parabolic antennas, and require line-of-sight clearance) except that, with microwave, the antennas are pointed at the horizon instead of at the sky; additionally, the distances involved are much shorter. Microwave transmission is considered to be a terrestrial means of communication. See also: backhaul, first mile, last mile, telephone line
Mode :
In analog audio, the nature of the audio signal (either mono or stereo) represented as “channels.”
Model :
A model is a complete description of a system from a particular perspective (“complete” meaning that you don’t need any additional information to understand the system from that perspective). See also: Rational Unified Process
Modulation :
The act of encoding or impressing a video, audio, or data signal onto a carrier such that it can be sent somewhere else by a transmission system. In the PRSS, analog audio signals modulate the frequency output of one or more modulators whose outputs are sent to the satellite and ultimately received at the downlink sites. See also: bandwidth, carrier, channel format, demodulator, deviation, frequency, modulator, modem
Modulator :
A piece of equipment used at an uplink to generate a carrier of the proper frequency for transmission and to modulate it with the video, audio, or data signal that needs to be sent. “Fixed” or “fixed-tuned” modulators can only generate a carrier at one frequency. “Fully agile” modulators can generate a carrier on any frequency that can possibly exist on a satellite transponder (one frequency at a time). A separate modulator is required to transmit each carrier that must be originated simultaneously at an uplink. Modulators also have “channel formats.” See also: channel format, demodulator, modulation
Modulator/ Demodulator (Modem):
Any device that allows two computers or other digital devices to exchange data by means of modulating the data stream onto a carrier of some sort and then demodulating the desired information from the carrier at the distant end.
Monitoring :
The act of listening to a feed as it is being played back, fed, transmitted, or recorded to check for quality or transmission problems. Similarly, the act of watching the satellite spectrum analyzer to check for transmission problems.
Mono :
A single channel with all audio information contained within it. See also: mode, stereo
Multicast :
Communication between a single sender and multiple receivers on a network.
Multiple Channels Per Carrier (MCPC):
A satellite communications system in which each radio frequency carrier contains multiple audio or data channels. A receiver must be able to parse the signal in order to extract a particular channel for use. See also: multiplexing, SCPC
Multiple Reel Format :
A taped program is fed with a predetermined start time for each reel and several minutes of silence between reels to allow stations recording the feed time to put fresh tape on the machine. See also: prefeed format
Multiplexing :
Combining multiple signals into a single signal for transmission. Requires demultiplexing at the site of reception.
MyContent Exchange Page :
The personalized web page for content exchange. This page can be customized by each station or producer. See also: content exchange
Narrowband (NB):
See also: bandwidth
Negative ACKnowledgment (NAK):
A communications control character sent by a receiving station to indicate that the last message or block received was not received correctly. See also: ACK
Network Address Translation (NAT):
An Internet standard that enables a local area network (LAN) to use one set of IP addresses for internal traffic and a second set of addresses for external traffic. See also: LAN
Network Agent :
A device, such as a router or workstation, that is equipped to gather performance information to send to the network management agent.
Network Control Center (NCC):
A central location on a network where remote diagnostics and network management are controlled.
Network Management System (NMS):
The system responsible for managing a portion of a network. The NMS talks to network management agents, which reside in the managed nodes, via a network management protocol. The NMS is the entity that implements functions at the network management layer.
Network of Interest (NOI):
A named group of station addresses, similar to an email distribution list. NOIs are used in the DACS and demodulator authorization systems. See also: DACS
Network Operating Center (NOC):
The central control and operations point for ContentDepot file transfer and streaming functions. See also: ContentDepot, file transfer protocol, System Technical Center
Network Service Provider (NSP):
A company that provides backbone services to an Internet service provider (ISP). See also: ISP
Not Applicable (N/A):
Not available.
Notification Input :
A user-defined message associated with a GPI status input from a specific non-programming device, such as a fence alarm. Notification inputs are defined in the Setup program, and the message (if activated) appears on the SOSS computer display. See also: GPI, SOSS
NPR Operator :
NPR personnel authorized to control the operation of the ContentDepot. See also: ContentDepot
NPR Satellite Services :
The unit of NPR Distribution that markets excess capacity on the PRSS. The revenue earned from this activity helps to reduce the operating costs of the system for public radio users.
Open Database Connectivity (ODBC):
A programming interface that provides a common language for Windows applications to access databases on a network.
Open Systems Interconnection (OSI):
A reference model developed by the International Standards Organization (ISO) for communication between different systems made by different vendors. See also: ISO
Operating System (OS):
The main control program of a computer that schedules tasks, manages storage, and handles communication with peripherals.
Operations Schedule (OPSKED):
A satellite schedule transmitted by DACS showing a two-day period of time. The operations schedule lists programs and their start and end times. It is sent to stations one to two days ahead of time. See also: transmission schedule
Operator Action Display (OAD):
Custom software application used to view and control, in real time, the progress of scheduled transmissions that are currently active or due to start within the next two hours. This is the main control panel for the ARA system. See also: ARA
Origination Site :
The origin of a remote broadcast. For a live symphony performance, the origination site might be the local concert hall. The first mile connects the origination site to the uplink. See also: first mile
Package :
A collection of classes, relationships, use-case realizations, diagrams, and other packages; it is used to structure the design model by dividing it into smaller parts. Packages are used primarily for model organization and typically serve as a unit of configuration management.
Packet Data Unit (PDU):
Also referred to as protocol data unit. OSI (open systems interconnection) terminology for a generic “packet.” A PDU is a message of a given protocol comprising payload and protocol-specific control information, typically contained in a header. PDUs pass over the protocol interfaces that exist between the layers of protocol (per OSI model). See also: OSI
Parabolic Reflector :
A surface that reflects, to a single focal point, all waves arriving from a direction parallel to its axis. Therefore, it is useful as a microwave antenna, which includes satellite communications when a feed (or subreflector) is placed at the focal point. See also: antenna, feed element
Participating Station :
An interconnected public radio station that enjoys the full rights and privileges of participation in the PRSS. See also: contributing station
Perceptual Coding :
A process that reduces the data rate of a digital signal through lossy techniques based on the masking properties of human auditory perception. See also: compression, data reduction, MUSICAM
Phase Shift Keying (PSK):
A modulation method, somewhat analogous to FM, in which the instantaneous transmitted phase of the carrier indicates the digital data being sent. Virtually all digital satellite communications use a form of PSK modulation. Sometimes called phase modulation (PM). See also: 8 phase shift keying, FM
PJ-11, PJ-45 :
Plug for an RJ-11 o RJ-45 modular jack.
Plain Old Telephone Service (POTS):
The basic dial-access voice service available from the public switched telephone network.
Point of Presence (POP):
An access point to the carrier or a service provider through which all local telecommunications service and equipment connects to the network backbone. A point of presence is a physical location, either part of the facilities of a telecommunications provider that the ISP rents or a separate location from the telecommunications provider, that houses servers, routers, ATM switches and digital/analog call aggregators. See also: POP
Point of Service (POS):
Also known as point of presence (POP).
Port :
A connection point on a computer or other device to which an external device can be connected.
Portal :
A website or service that offers a broad array of resources and services via a single, unified interface.
POTS Bridge :
“Plain Old Telephone Service” conferencing bridge. Services provided by a vendor that allows multiple callers to make a phone call using a standard telephone and while simultaneously listening to the same audio. The PRSS will use a POTS Bridge as the first level of program restoral in the event of a satellite outage.
Power :
The attribute that determines a channel’s signal strength on a satellite transponder. More power means a less noisy channel, which can carry higher quality audio or higher speed data. In satellite communications, power is measured in dBW. Each of the occasional service public radio channels operates at a power level of 16 dBW. See also: bandwidth, channel format, frequency
Precipitation Scatter :
The radio interference effect caused when precipitation in the form of rain, snow, sleet or hail falls into the intersection of two antenna beams, thus causing an unwanted signal to be reflected into the receive antenna.
Prefeed :
A feed of a program that precedes the program’s release date (date that stations may begin using the program over their local air). See also: alternate feed, makegood, refreed, repeat, retransmission
Prefeed Format :
See also: multiple reel format
Producer :
An entity that develops radio programs to be distributed to stations.
Production Feed :
Any transmission of audio material intended for insertion into another program. Generally, only needs to be received by one downlink. Also known as a “backhaul” or “point-to-point.” See also: backhaul, two-way
Program :
A radio show or series. Examples include Morning Edition, A Prairie Home Companion, or This American Life.
Program ID Code (PID):
The identifying number assigned by the PRSS scheduling system to each program for transmission. It consists of a two-digit year code, a three-digit series code, and a five-digit episode code.
Program Stream :
The flow of bits that comprise a streamed radio program.
Public Broadcasting Core (PBCore):
The metadata scheme that will facilitate the distribution of content to diverse audiences across a variety of media. This model is being created by the Metadata Model Project, an industry-wide initiative that was launched in spring 2002. NPR Distribution is participating in the project as a member of the Metadata Working Group. See also: metadata
Public Radio Account Representative :
In the PRSS, the public radio account representative works with producers to schedule programs on the standard public radio channels.
Public Radio Satellite System (PRSS):
The distribution network through which thousands of hours of news, music, and specialized audience programming are delivered every year to public radio stations throughout the United States.
Public Switched Telephone Network (PSTN):
The network of cables, switching centers, and telephone companies that provide basic switched voice grade telephone service to homes and businesses worldwide. See also: POTS
Public Telecommunications Entity (PTE):
A public broadcast station or a noncommercial enterprise that is owned and operated by a state, public agency, nonprofit private foundation, corporation, or association, and is organized primarily for the purpose of disseminating to the public audio or video noncommercial educational and cultural programs.
Quadrature Amplitude Modulation (QAM):
A sophisticated modulation technique, or compression technique, that uses variations in signal amplitude and phase, which allows multiple bits to form a single “symbol,” which then is impressed on a single sine wave. “Quadrature” refers to the fact that four (i.e., “quad”) distinct amplitude levels are defined. See also: 16 QAM
Quadrature Phase Shift Keying (QPSK):
A method of phase-modulating a radio frequency carrier with digital information in which the instantaneous phase angle of the received carrier determines whether a bit combination of 00, 01, 10, or 11 is being received. There are four possible phase angles, 90 degrees apart. The audio and data channels in the PRSS use QPSK modulation. See also: BPSK
Quality of Service (QOS):
A measure of the service quality provided to a subscriber.
Radio Frequency (RF):
Any frequency that can be fed to a local antenna and radiated to a remote antenna to allow for communication over a distance. Generally, any frequency over about 30 kilohertz (30,000 vibrations per second). See also: audio frequency, baseband, IF
Radio Frequency Interference (RFI):
The reception of unwanted signals that may render the use of a satellite downlink terminal, or of any radio receiver, useless. This is avoided through frequency coordination. See also: frequency coordination
Rational Unified Process (RUP):
A software development approach that provides a structured framework for assigning tasks within a development organization. RUP employs an iterative and use-case driven process.
Real Time :
Execution or display of an event as it happens, without significant delay.
Real Time Streaming Protocol (RTSP):
An application-level protocol for control over the delivery of data with real-time properties.
Receive Address :
The unique address of each station in the ContentDepot system. This allows content to be addressed to each station or groups of stations. See also: ContentDepot
Receive and Transmit (R/T):
Refers to a satellite earth terminal that has both uplink and downlink capabilities. See also: antenna, uplink
Receive Only (R/O):
Refers to any satellite earth terminal with only downlink capability. See also: antenna, downlink
Receiver :
Any entity that receives programming or other material through the PRSS. This typically refers to a station.
Receiver Control Messages :
Messages sent to a receiver to control how it filters and routes content.
Reception :
The capacity of a device to receive content from the PRSS.
Record :
This refers to the ability of a device to encode an audio stream and save it as an audio file for storage and playback at a later time.
Reed Solomon (code) (RS):
A means of accomplishing forward error correction (FEC) in order to compensate for errors bursts created in data transmission. See also: FEC
Refeed :
An extra feed of a program, requested by a receiving station due to a technical or operational failure during local recording of the primary feed. See also: alternative feed, makegood, prefeed, repeat, retransmission
Refeed Request Number :
A special three-digit code that station managers or program directors are given to use when requesting refeeds from NPR Distribution. This number gives station management the ability to allow as many or as few employees as desired the means to request refeeds, for which the station is billed.
Reference Architecture :
A reference architecture is, in essence, a predefined architectural pattern, or set of patterns, possibly partially or completely instantiated, designed, and prove for use in particular business and technical contexts, together with supporting artifacts to enable their use. Often, these artifacts are harvested from previous projects. See also: Rational Unified Process
Registered Source :
A person or organization that registers to use services from NPR Distribution.
Registration :
The action taken by the FCC for satellite downlinks. In conjunction with frequency coordination, registration protects earth terminals from interfering sources. Also, the process by which program distributors are granted the ability to schedule programs on the satellite. See also: FCC, frequency coordination
Repeat (RPT):
A regularly scheduled additional feed of a program. See also: alternate feed, makegood, prefeed, refeed, retransmission
Requirement :
A requirement describes a condition or capability to which a system must conform, either derived directly from user needs, or stated in a contract, standard, specifications, or other formally imposed document. See also: Rational Unified Process
Resource :
A station device defined and configured (using the SOSS setup program) for the purpose of carrying out an event in the local transmission schedule, as defined in the schedule editor. A resource can be classified as a source (outputs audio), a destination (receives audio), or both. It can be one of these types: demodulator, storage (such as tape decks), or general (such as telephone lines, smoke alarms, etc.). For a resource to actually communicate with the SOSS computer, it must be connected to the serial control bus. See also: schedule editor, serial control bus, SOSS
Resource Conflict :
In the schedule editor, a resource conflict occurs when one or more resources for an event are already allocated for a specified time period. To schedule the new event, one must modify either the existing event or the one that is being placed into the transmission schedule. See also: schedule editor
Resources :
The equipment available for recording, playing, or routing audio feeds or files. Resources include CD decks, DAT machines, tape decks, and available ports.
Retransmission (RETRANS):
An extra feed of a program, requested by the distributor, usually due to a technical or operational problem on the distributor’s part in supplying the program to the system. See also: alternate feed, makegood, prefeed, refeed, repeat
Role :
A role defines the behavior and responsibilities of an individual or set of individuals working together as a team, within the context of a software development organization. A role is responsible for one or more artifacts and performs a set of activities. See also: Rational Unified Process
Rotating Head Digital Audio Tape (RDAT):
See also: DAT
Sampling Rate :
The rate at which analog signals are examined or sampled for encoding into a digital form. The higher the sampling rate, the more accurate the digital representation of the analog signal. Examples: 44.1 kHz; 48 kHz.
Satellite :
Any object in orbit around the earth. In broadcasting, the term refers specifically to “geostationary communications satellites,” which, unlike some military and weather satellites, remain parked in a fixed position relative to a spot on the ground. A satellite has an average lifespan of ten to twelve years, limited mainly by the supply of fuel required to maintain its position in space. Satellites operate on two frequency bands known as “C-band” and “Ku-band.” See also: C-band, geostationary orbit, Ku-band, transponder
Satellite Delay :
The time it takes for a signal that leaves an uplink to arrive at a downlink. For one-hop satellite transmissions the delay is about ¼ second. See also: double hop, hop
Satellite Interconnection Agreement (D/I Agreement):
The contract between NPR and a public radio station which defines the rights and obligations under which a station is provided service through the PRSS. All stations acquiring programming via the public radio transponder are required to sign this agreement and pay an annual D/I fee which represents a share of the cost of operating and maintaining the system. See also: D/I fee, interconnected station
Satellite Operating Support System (SOSS):
An integrated collection of equipment, computer programs, and data that makes operation of the PRSS more convenient for distributors and interconnected stations. The SOSS consists of DACS, ARA, the DSC, the STC’s automation control system, and Distribution’s scheduling and billing subsystems. See also: ARA, DACS, DSC
Satellite Schedule :
The collection of confirmed occasional service radio programs and the satellite channels and dates and times on which they’re scheduled to be broadcast to interconnected stations. See also: advance scheduling, operations schedule, transmission schedule
Satellite Transmission :
In the ContentDepot system, a satellite transmission represents each specific content delivery from the central platform, regardless of type. Currently, there are three types, live program, stored program, and content exchange. These are represented in the station platform as transmission streams (for live programs) and stored transmissions (for stored programs and content exchanges). The key difference between stored programs and content exchanges is that the transmissions for stored programs are scheduled and the default station schedule may or may not differentiate between the two. See also: central platform, ContentDepot
Schedule Editor :
PRSS custom software application that fully automates the execution of the local transmission schedule over the equipment at stations. Generally, two kinds of activities are performed: planning the programming schedule by selecting PRSS transmissions and by adding local programming; and assigning station resources (demodulators, tape deck, etc.) to transmissions in the local station schedule. The ARA system continuously reads and executes the events in the local schedule. See also: ARA, ContentDepot
Scheduled Delivery :
Represents the scheduled event for the delivery of a program episode and the resources necessary to transmit the content for that program episode.
Scheduled Ingest :
Represents the scheduled event for the intake of a program episode and the resources necessary to receive incoming content for that program episode.
Scheduling Record :
In the ContentDepot system, a data file sent from the information system to the central platform that indicates how a program file should be processed. See also: central platform
Secure Sockets Layer (SSL):
The leading security protocol on the Internet. When an SSL session is started, the server sends its public key to the browser, which the browser uses to send a randomly generated secret key back to the server in order to have a secret key exchange for that session.
Segment :
An individual content section of an episode bounded by breaks for local station insertions. For example, pre-recorded episodes may consist of multiple files (segments) so that stations can insert content in an automated fashion.
Segue :
A direct transition between audio segments at full volume. Also known as a “cut” or a “switch.” One alternative to a segue would be a crossfade, where the first segment volume is fading as the second segment volume is increasing, mixing the sound from the two segments.
Serial Control Bus (SCB):
The cable system that interconnects SOSS equipment and station equipment, thus enabling remote control and automation. Uses RS-485 protocol to carry control and status information. One’s system can have up to six distinct serial control buses branching off the ARTIC card. See also: ARTIC, SOSS
Series :
A group of related programs; a collection of episodes. All programs in a series share a common series title and series number, although each program has a unique episode number and may or may not have a unique episode title.
Service Charge :
A charge that is assessed to program distributors who request cancellation or modification of a scheduled program or series after confirmation.
Service Level Agreement (SLA):
A contract between a network service provider and a customer that specifies the services the network service provider will furnish.
Shadow Use Case :
Use cases that meet all of the criteria of typical use cases but are not describing functions for the end user, but for the staff who will have to manage the system. The most typical shadow use cases are archiving, security, and maintenance. See also: use case
Shared Web Hosting :
Web hosting where several customers share the same server leased by the hosting provider.
Simple Network Management Protocol (SNMP):
The most common method by which network management applications can query a management agent using a supported MIB (management information base). SNMP operates at the OSI application layer. The IP-based SNMP is the basis of most network management software. See also: MIB
Simulcast :
Simultaneous broadcast of the same program by local radio and television stations, such that viewers/listeners can watch television and receive the sound portion of the program over high-quality FM stereo. PBS and NPR Distribution cooperate in networking several simulcasts each year.
Single Channel Per Carrier (SCPC):
A satellite communications system in which each radio frequency carrier contains one audio channel. Two different carriers are required for stereo audio. While the digital carriers on the PRSS are often referred to as SCPC carriers, they are more accurately single program per carrier, because a stereo program can be transmitted in a single carrier.
Solar Outage :
The temporary failure of a downlink caused by the electromagnetic energy of the sun overpowering the signal from a satellite as it passes directly behind the satellite. This phenomenon happens twice each year for about five days, up to six minutes per day, and is predictable. Solar outages affect downlinks only, not uplinks. If an uplink station is experiencing a solar outage (making its own downlink unusable) it can still uplink interference-free signals to other downlinks that are not being affected at that time. See also: downlink, uplink
Space Segment :
The satellite transponder (or portion of a transponder) used to complete a transmission. See also: ground segment
Spectrum :
A representation of frequencies, arranged in ascending order from lowest to highest. See also: frequency, spectrum analyzer
Spectrum Analyzer :
An electronic device that presents a visual display of the satellite spectrum and the bandwidth, power, and frequency of each channel. See also: bandwidth, channel, channel format, frequency, power, spectrum
Stakeholder :
A stakeholder is an individual who is materially affected by the outcome of the system. See also: Rational Unified Process
Standard Compressed Format :
A format used in the delivery system to stream compressed audio over the MCPC satellite uplink. See also: MCPC
Standard Recording Format :
A list of requirements stating how a recorded program is to be prepared for transmission by its producer before it is delivered to a public radio uplink.
Station Archive :
A database in the ContentDepot station platform used to store radio files extracted from a broadcast channel. See also: ContentDepot, station platform
Station Audio Equipment :
Equipment at a station used to store and route audio signals within the station in the ContentDepot system. See also: ContentDepot
Station Controller :
A software device that coordinates and commands all of the other devices on the station platform to initiate functions such as receive, record, store, play, and decode. The station controller receives its instructions from the station schedule and any-time critical messaging. See also: ContentDepot
Station Equipment :
Any interconnected equipment supplied by the station. Can include the following: analog and digital audio equipment (tape machines, digital audio tape, hard disks, live broadcast); other peripheral devices (on-air lights, housekeeping alarm indicators); other audio sources (studios, telephone lines); etc.
Station Log :
A list of activities (confirmations of transmissions, errors, etc.) that occur at the station.
Station Operator :
Station personnel responsible for the operation of the station platform. See also: station platform
Station Platform :
The hardware and software provided by NPR to enable a station operator to control the selection, storage, and routing of content transmitted from the STC. See also: station operator
Station Receiver :
An interface within the system that is part of the station platform for receiving content. See also: station platform
Station Schedule :
Defines the date and time that each program will air, as well as what station resources will be used to play the signal to air.
Status Inputs :
Any pair of GPI terminals labeled “status input” that receives some sort of status information from a connected device (such as a tape deck). Status inputs can be used to report to the SOSS computer availability, ready state, inhibit state, a cue such as an out-of-tape marker, alarm status, or some other information. See also: GPI
Stereo :
Two channels where the special characteristics of the recorded audio signal are represented across the channels. In digital audio, “stereo” can take additional forms: “joint,” where common information from each channel is shared between the two to reduce the amount of digital bandwidth required to represent the signal; and “discrete,” where the digital information of the two channels remains separate (also known as dual mono). See also: mode, mono
Storage :
The capacity of a device to retain and hold data.
Storage Resource :
Any device controlled by the ARA that records or plays back audio transmissions. For example, a tape deck and a DAT. See also: ARA, resources
Stored Content Confirmation :
In the ContentDepot system, refers to the station platform's ability to communicate with the central platform to confirm that each stored program has been received intact and uncorrupted. See also: central platform, station platform
Stream :
A compressed, digitally encoded representation of a radio program broadcast in a format ready for real time decoding and immediate playback. See also: streaming
Streaming :
An Internet data transfer technique that allows the user to see and hear audio and video files without lengthy download times. The host or source "streams" small packets of information over the Internet to the user, who can access the content as it is received. Streaming is accomplished by way of web browser plug-ins, which decompresses and plays the file in real time. See also: stream
Structured Query Language (SQL):
A language used to interrogate and process data in a relational database.
Sub-Package :
A subset of a package. See also: package
Subscription :
The process by which an interconnected station searches for, auditions, and selects programming that will be delivered via the ContentDepot. See also: ContentDepot
Sun Transit Outage :
See also: solar outage
Switched 56 (SW56):
A digital means of sending audio of better than voice grade through a special kind of dial-up telephone call. To accomplish Switched 56 transmission, users at both ends must have the proper CODEC device and both must have a special digital telephone called a digital service unit (DSU). In addition, each end must have a special, digital dial-up telephone line called a Switched 56 circuit. A call is dialed up from one end to the other and an audio chain of 7.5 kHz quality is established in both directions. Switched 56 has been made mostly obsolete by the widespread adoption of ISDN. See also: CODEC, decoder, DSU, encoder, ISDN, T1, telephone line
Switcher Cross Points :
The input and output ports of an audio switcher that connect to a particular device. These are defined in the SOSS setup program for each resource that is connected to an audio switcher. See also: resource, SOSS
Synchronous Transfer Mode (STM):
A transport and switching method that depends on information occurring in regular and fixed patterns with respect to a reference such as a frame pattern.
System Schedule :
See also: transmission schedule
System Technical Center (STC):
The coordination and monitoring facility for the public radio distribution system. Located at NPR headquarters, the STC supervises all satellite carriers on the public radio system and all public radio uplink program traffic, delivers data services provided over the DSC, and operates the Washington, DC uplink. See also: Network Operating Center
System Uplink :
An uplink terminal capable of radiating to the public radio satellite transponder(s) and which has signed an origination terminal operator’s agreement with NPR Distribution.
T1 :
A multiplexing arrangement that divides a single 1.44 MHz carrier into up to 24 voice, program, and/or data channels. A T1 carrier can be sent over microwave, satellite, or fiber circuits and is a common method of combining multiple signals for transmission. See also: digital signal level (X), ISDN, switched 56, telephone line
Telephone Line (Telco):
Also called “telco line” or “loop.” A means of sending audio signals over short or long distances using special analog “program circuits” supplied by telephone companies. See also: backhaul, fiber optic, first mile, last mile, microwave
Teleport :
An uplink/downlink equipped to handle multiple audio, video, and data feeds to and from more than one satellite simultaneously. Teleports are usually located in the suburbs of major cities, are privately owned for profit, and market themselves as a gateway, providing service between the city near them and all other cities in the nation or world.
Terminal Adapter (TA):
A customer service unit that is used on an ISDN line as an interface between the line and the CODEC. This equipment coordinates timing and protocols between the line and the CODEC and coordinates the combining of the ISDN B (bearer) channels. See also: CODEC, CSU/DSU, ISDN
Terrestrial :
Generally refers to any means of transporting audio, video, or data along the surface of the earth without using satellites. Point-to-point microwave systems, telco lines, and fiber optic systems are all terrestrial. See also: fiber optic, microwave, satellite, telephone line
Terrestrial Interconnect Link :
The land-based link between an earth terminal and the studio. It may be a cable system, a microwave system, or telephone company analog or digital lines.
Time Division Multiple Access (TDMA):
A technique originated in satellite communications to interweave multiple conversations into one transponder so as to appear to get simultaneous conversations.
Time Division Multiplex (TDM):
A technique for transmitting a number of separate data, voice, and /or video signals simultaneously over one communications medium by interleaving a piece of each signal one after another.
Transaction Record :
In the ContentDepot system, a record of key transactions at the station platform that is sent to the central platform. See also: central platform, station platform
Transmission :
The process of sending content (to include programs and metadata) over satellite or the Internet to be distributed to stations. In terms of the ARA, a distinct occurrence of a program broadcast over the satellite. See also: ARA
Transmission Control Program/Internet Protocol (TCP/IP):
A networking protocol that provides communication across interconnected networks, between computers with diverse hardware architectures and various operating systems.
Transmission Control Protocol (layer 4) (TCP):
A transport layer, connection-oriented, end-to-end protocol. It provides reliable, sequenced, and unduplicated delivery of bytes to a remote or local user.
Transmission ID :
A sequence of numbers that is attached to and uniquely identifies each content item sent through the ContentDepot system. See also: ContentDepot
Transmission Schedule :
In general, a listing of transmissions that are scheduled to be aired. The ARA system employs two kinds of schedules, system and local. The system schedule consists of all upcoming PRSS transmissions available to a station. The local schedule is the list of transmissions that actually trigger events at the station. It consists of those PRSS transmissions that have been chosen from the system schedule, as well as transmissions that originate at the local station. Also, a portion of satellite schedule transmitted by DACS showing a one-week period of time. The transmission schedule lists programs, their start and end times, and other program-related information. It is sent to stations one week in advance. See also: operations schedule, satellite schedule
Transponder :
A portion of a satellite’s total signal-carrying capacity. Most communications satellites are divided into 24 transponders of equal bandwidth. A transponder can transmit video signals with audio subcarriers or may be used for digital or analog audio distribution of between 20 and 100 channels (per transponder) depending on transmission format. See also: bandwidth, RF, satellite
Turnaround Site :
An uplink/downlink used as part of a double hop because of its ability to receive a signal from one satellite and to retransmit it to another. See also: double hop
Two Degree Spacing :
In the mid-1980s, the FCC decided that satellites should be spaced two degrees apart in the geostationary orbit in order to increase the number of satellites in operation to meet expected future service demand. See also: geostationary orbit
Two-Way (2WY):
A special kind of production feed in which a reporter and a guest are in