SUPPORT>GLOSSARY
 













 




ADC Analogue Digital Converter; converts analogue signals into digital input.
  A/B Switch A switch that selects one of two inputs (A or B) for routing to a common output while providing adequate isolation between the two signals.
  Adjacent Channel An adjacent channel is one which is immediately next to another channel.
  AFC A circuit which locks an electronic component onto a chosen frequency.
  A.G.C. Controlling the gain of a device by the signal level through the device (using a high gain feedback loop circuit). A rising input signal level produces a negative feedback signal, which lowers the gain. A circuit that uses feedback to maintain the output of an electronic component at a constant level.
  Agile Component A component which can be tuned to any desired channel.
  Amplifier A device used to increase the power of a signal.
  Analog A system in which signals vary continuously in contrast to a digital system in which signals vary n discrete steps.
  Antenna A device that contributes an energy gain. Satellite dishes, broadband antenna and cut-to-channel antennas are some types of antennas encountered in private cable systems.
  Antenna Pre-Amplifie An amplifier located in the immediate vicinity of the antenna, used to amplify extremely weak signals, thereby improving the signal-to-noise ratio of a system.

  Base connection ISDN connection with SO interface which consists of 2 data channels (B channels) with 64Kbps and a data channel (D channel) with 16 Kbps.
  B Channel Channel for transmission of ISDN user-data with a transmission speed of 64kbit/s.
  B Frame Bi-directional Frame - this type of frame is produced in MPEG encoding, and can only be encoded if the previous and following frames are also known.
  BISYNC Binary Synchronous Communication - a transmission protocol for synchronous (binary) data transmission.
  BRI Basic Rate Interface - the international term for the basic ISDN connection.
  Bridge Connection between two or more networks. Can only be networks with the same topology (e.g. Ethernet) and the same protocols.

  Cache Buffer memory which can be installed between different kinds of memory media. Intermediate storage in a cache reduces the access speed.
  CAPI Common ISDN-API - the standardised interface for ISDN cards.
  Channel bundling The combining of several B-channels which together form a virtual channel with a higher data transmission rate, especially valuable for video-conferencing and video phones.
  Cinch Two-pin plug connection for transmission of audio and video information.
  CODEC Coding/decoding and compression/decompression of video conferencing signals according to a particular procedure. The process has been standardised by the ITU. The conversions are done using a special CODEC card which usually includes communication interfaces (ISDN/LAN).
  Continuous Presence (Quarter Split) A form of multipoint conference in which people in 5 locations can participate via picture and sound. With this each screen is split into 4, each sector showing a different location.
  CPU-Bus Internal management system through which the processor exchanges data with its environment.
  CVBS Signal A video signal including color, picture, blanking, and synchronisation information, produced by video recorders and camcorders which operate according to the Video 8 or VHS standards and in which brightness and color are transmitted in parallel.

  Data compression A means of increasing the effective data transmission performance. Data are compressed using special mathematical processes.
  DCT Discrete Cosinus Transformation - a process for data reduction, predominantly for M-JPEG. Individual pictures are divided into blocks of 8x8 pixels and simplified colour information allocated to them.
  DDC Dynamic Data Channel - is a protocol for data communication between video conferencing systems.
  DECT Digital European Cordless Telecommunication - is the European digital transmission standard for cordless telephones.
  D Channel In ISDN, a channel for the transmission of service information. All the relevant signals for connection and disconnection of the link are carried in the D channel. 1TR6 and DSS1 are different and non-compatible D channel protocols.
  Downspeeding A safety function which is triggered when one part of the B channels used for communication fails, and this ensures that the transmission is not completely interrupted.
  DSS1 Digital Subscriber Signalling System No.1 - a signalling protocol used between the ISDN terminal devices and the PBX.
  DSP Digital Signal Processor or single chip microcomputer which is used in electronic systems to control independent processes and take on computational tasks.
  DSVD Digital Simultaneous Voice Data - a modem which supports both data transmission and voice communication at the same time.
  DTMF Dual Tone Multi Frequency - dialling and controlling signals in the form of combinations of tones.
  DVI Digital Video Interface - where video pictures are digitised in real time and saved as compressed video files.

  Echo Suppression A system for filtering the echo feedback which occurs with speech transmission. This considerably improves the quality of the voice transmission.
  Encryption/decryption Encryption/decryption is used to ensure that data communications cannot be eavesdropped. The encryption systems have to be installed at both transmitter and receiver sides.
  Ethernet An electronic data processing network which nowadays is the most widely used system for local networks

  FDDI Fibre Distributed Data Interface - interface for data which is transmitted in light waves by fibre optic cable. High speed technology based on the Token ring principle.
  Firewall A firewall seals off data networks. Any data going into or out of the network must pass through the firewall and only the data which complies with security requirements is allowed through.
  Fixed Link Permanent active connection between two sub-networks within in the network. No other users can use this connection.
  Frame A frame is an single picture within the body of video data.
  Frame Rate With digital video this is the picture refresh rate. To achieve a full motion video a frame rate of 25 frames per second is required. With less than 15 frames per second the video movement is jerky.
  Full Duplex refers to the ability to send and receive data simultaneously at maximum speed.

  Gateway In video conferencing these allow H.323-compatible systems to communicate with H.32x terminals. For example a gateway system can link an H.323 system with H.320 (SIDN), H.321 (ATM), H.322 (ISO Ethernet) or H.324 (PSTN). At present an H.323 to H.323 connection (LAN/LAN) is still the most used form of VC gateway.
  Genlock Generator Lock - in analogue systems this is how the video signal is fed into the PC. Using Genlock the video signal can also be blended with a graphic or with another video signal and then be put on tape.
  Grabbing This relates to the grabbing and storage of picture data on the computer. There are various grabbing functions: screen grabbing, frame grabbing, motion grabbing. (Screenshots are individual pictures taken from the video sequence.)
  GSM Global System for Mobile Communications - international standard for the digital mobile radio telephone network.

  H.320 The ITU-T (International Telecommunication Union) standard for picture and sound communication over ISDN.
  HDLC High-Level Data Link Control - transmission protocol
  Highlight-Compression-System Special peripheral circuit for smear suppression and to give full detailed picture reproduction of extremely bright areas.

  ICM Intelligent Call Management - this function dynamically distributes and manages the transmission bandwidth between video, audio and data.
  IMUX Inverse Multiplexer - a device for managing transmission when using several ISDN channels for video or data communication.
  Interface Interfaces allow the communication between different kinds of hardware and software, and between users and programs.
  Inter-Frame Compression A process for compressing digital videos in which only the changes between sequential pictures are saved. - Whereas with intra-frame compression only the data within the frame is reduced.
  ISDN Integrated Services Digital Network.

  LAN Local Area Network - the networking of computers within a limited area.
  LANC Local Application Control BUS System - interface for controlling video recorders and camcorders.
  LapLINK A special program for data exchange between two PCs via serial or parallel ports or an ISDN card.
  Low Frequency Signal Level Low frequency signal level (linein/lineout).

  MCU Multipoint Control Unit - a system which enables and controls a conference with more than two participants.
  MIDI Music Instruments Digital Interface - software interface for the exchange of data between a musical instrument (keyboard etc.) and a computer.
  MJPEG Motion Joint Photographic Experts Group - a digital editing compression procedure for the storage of video sequences. Whereas with MPEG (Moving Pictures Experts Group) only the differences between individual pictures are saved, here each picture is retained.
  MSN Multiple Subscriber Number - number with many devices connected.
  Multiplexer Device for recording signals from up to 16 cameras using only one video recorder. Can provide full-screen replay of individual chosen cameras as well as multi-screen displays.

  NDIS Network Driver Interface Specification - definition of interface between the local network operating system and the network adapter.
  NetMeeting Microsoft NetMeeting 2.0 enables users all to benefit from audio, video, data and applications in real time over various kinds of link. The functions available vary according to the kind of connection. For connections between two modems, data and applications are supported but audio and video are not. The same is true for connections in local networks (IPX/SPX-LANs). A TCP/IP connection or a local area network (LAN) is needed to support audio and video.
  NT Network Terminator
  NTBC Network Terminal Base Connection, the connecting element between the ISDN circuit and the user connection.
  NTSC National Television System Committee - the American TV standard (power supply frequency 50 Hz, 525 lines, 30 pictures/s). PAL, the European standard and SECAM, the French standard, have 625 lines and 25 pictures/s.

  ODAPI Open Database Application Programming Interface - software interface controlling the data exchange between databases and other applications.
  OSI- Layer Model Open Systems Interconnection (OSI) - is an ISO working group which lays down general standards. The Open Systems layer model specifies the handling and management of data transmission in a network which is divided in to different levels or layers.

  PAL Phase Alternation Line - the European video standard (50 Hz power supply).
  PBX Private Branch Exchange; private telecommunications exchange.
  PCI Peripheral Component Interconnect - bus format for computer cards.
  PCM Process Pulse Code Modulation - a process for converting analogue signals into digital information, e.g. for digitising audio data.
  PDN Public Data Network.
  PPP Point to Point Protocol - serial transmission protocol for point to point connections, for example for access to the internet using a modem.
  POTS Plain Old Telephone Service - analogue telephone network, using for example twisted pair cabling for modulated voice signals.
  PSTN Public Switched Telephone Network - (fixed) analogue telephone network.

  Quad Unit For simultaneous display of four camera pictures on one monitor.
  Quality of Service This ensures an application is allocated specific necessary network resources in the form of a guaranteed bandwidth - an important consideration with video conferencing and voice over IP (VoIP).

  RCTC Timecode Rewriteable Consumer Timecode - for linear cutting in video editing.
  Remote Management Remote control of devices.
  RMA Testcard Radio Manufacturer Association Testcard - test card or slide for testing camera quality.
  RNA Remote Network Access.
  Router A special device for forwarding data packages to the appropriate junctions and intersections in the network and thus linking the network together. The network topologies can be different (e.g. Token Ring and Ethernet).
  RS232-Interface This is the computer connection where the mouse and the modem are plugged in. Only 9 and 25 pin connections conforming to the V.24 standard can be made with this kind of interface .

  Sampler A device for converting data (usually audio) into digital data. These data can then be processed in a PC. Sampling refers to the digitisation of graphics (using a graphics card) and notes, speech and sounds (using a sound card).
  Scart The standard socket used in TV and video.
  SCSI Small Computer System Interface - standardised interface for small computer systems to which peripherals (e.g. a CD drive) is connected.
  S/PDIF A digital audio interface which is connected to a digital audio device (e.g. DAT recorder) and enables copies to be made without any losses.
  S0 Interface The internationally standardised interface for ISDN end-user applications. It consists of two data channels (B channels) and a signal channel (D channel). Up to eight devices with 12 ISDN sockets can be linked to the SO interface.
  S2M Interface Basic ISDN connection (also primary multiplex connection) consisting of 30 user channels (B channels), one control channel (D channel) and a synch channel. Of the 32 channels, 30 are available for telephone use. (Interesting for larger firms).

  TCP/IP Transmission Control Protocol/Internet Protocol - TCP is responsible for the correct delivery of the data packets, IP for the transportation.
  TFT Display Thin Film Technology - the term used to describe flat screens with active internal illumination.
  Thumbnail In the video editing program this is the first frame which is used to represent the video clip.
  Time Multiplex Process Controls the transmission of different sources via a single transmission medium (serial circuit). A multiplexer allocates each source a time window in which digital data transmission is possible.
  Token Ring A special data packet which is passed from station to station in a Token Ring Network. The packet can only be forwarded by the current station so that there are no collisions in the transfer of information.

  V.24 is a control protocol for serial data transfer between a DTE (a piece of Data Terminal Equipment) and a DCE (a Distributed Computing Environment) - as between a computer and a modem. The term V.24 is often used to refer to an R232C interface.
  VBS Signal The name for a video signal produced by a black & white camera.
  VGA Video Graphics Array - the graphic standard used by all modern graphics cards (resolution up to 640x480 pixels).

  WAN Wide Area Network - the networking of PCs or local networks over public or private telecommunication networks.
  W.A.V.E. Camera Wide Angle View Camera - camera with a particularly wide field of view (wide angle lens + camera panning radius).
  White Value Limit Protection system for avoiding video signals levels above >1.1 Vpp.


  X.21 A transmission protocol, defining an interface in the physical layer. X.21 is used for X.25 networks.
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