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Industry terms defined...

Note: Many of these terms have different meanings, depending on the industry. The following glossary of terms is specifically associated with the visual and voice communications industry. If you do not find what you're looking for here, have further inquiries, or would like to suggest a new term and explanation, please contact us.

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AES: Advanced Encryption Standard. The highest level of embedded encryption security for videoconferencing. Security comes from the key, a number which is passed to the algorithm to tell it how to encrypt the data. A commonly employed communications encryption method is DES.

Algorithm: A step-by-step problem-solving procedure. Transmission of compressed video over a communications network requires sophisticated compression algorithms. Some videoconferencing systems offer both proprietary and standard compression algorithms.
Analog signals: Audio/video signals currently used in broadcasting where the signal is represented by variable measurable physical quantities (such as voltage). Current TV and radio signals are analog, as are many telephone lines. (Contrast with digital.)
Aspect ratio: The ratio of a picture’s width to height.  In video, this ratio is four units wide by three units high or 4:3. Widescreen, or 16:9 aspect ratio, is becoming more ubiquitous with the introduction of flat-panel displays (e.g. plasma, LCD) and HD videoconferencing.
Audio add-on: Allows a participant to join a videoconference via audio (telephone) only. This can be done through one of the codecs or through the video bridge.
Audio conferencing: Communication between three or more sites that are linked by a voice only telecommunications medium


B-channel: The Bearer ("B") channel is a 64 kbps channel which can be used for voice, video, data, or multimedia calls. B-channels can be aggregated together for even higher bandwidth applications.

Bandwidth: In casual use, the amount of information that can be transmitted in an information channel. High bandwidth Internet access means those web graphics load quickly on Netscape. High bandwidth videoconferencing means that the picture and sound will be clear. In computers, the speed at which data can be transmitted on a communications frequency. In telecommunications, the maximum frequency (spectrum) measured in Hertz or cycles per second, between the two limiting frequencies of a channel. In terms of videoconferencing (using IP or ISDN networks), the speeds or bandwidths usually run in increments of 64Kbps. 

For Example:

  • 64: 1x64Kbps
  • 128: 2x64kbps
  • 256: 4x64kbps
  • 384: 6x64kbps
  • 512: 8x64Kbps
  • 768: 12x64Kbps
  • 1024: 16x64Kbps or 1 MB (Megabyte)
  • 1536: 24x64Kbps or 1.54 Mbps (also known as a PRI line (ISDN) or a T1 circuit (IP))

Bit (binary digit): The smallest unit of information with two possible states. Examples include: one or zero, yes or no, on or off
bps: Bits per second (lower case is significant)
Bps or BPS: (8-bit) bytes per second (upper case is significant)
Bridge: See MCU
Broadband: A high-capacity communications circuit/path. It usually implies a speed greater than 1.544Mbps. (Contrast with wideband and narrowband.)
BRI: Basic Rate Interface (ISDN). Three digital signals over a single pair of copper wires: two voice (B) channels and one signal (D) channel. (e.g., voice and fax on a single pair of wires)


Camera presets: Allows pre-defined camera angles to be programmed into a videoconferencing system.

Codec: Coder/Decoder or Compression/Decompression. Videoconferencing hardware that codes the outgoing video and audio signals and decodes the incoming signals. Prior to transmission, the codec converts analog signals to digital signals and compresses the digital signals. Incoming audio and video must be decompressed and converted from digital back to analog.
Compressed video: When the vast amount of information in a normal television transmission is squeezed into a fraction of its former bandwidth by a codec, the resulting compressed video can be transmitted more economically over a smaller carrier. Some information is sacrificed in the process, which may result in diminished picture and sound quality.
Continuous presence: Conference allowing each site to view other sites on a screen. Sites can be viewed in multiple configurations of a split screen.


D-channel: The Delta ("D") channel can be either a 16 kbps or 64 kbps channel used primarily for communications (or "signaling") between switching equipment in the ISDN network and the ISDN equipment at your site.

Data rate: The measurement for bandwidth in bits per second. In general, the higher the data rate, the higher the quality of video.

DES: Data Encryption Standard. DES works by encrypting data with a 56-bit long key. Triple DES (3DES) is an enhancement to DES that effectively runs 112-bit long keys. DES and 3DES are both widely used in commercial and non-defense government communications today.

Desktop videoconferencing: Most appropriate for small groups or individuals (compare with room-based videoconferencing). Many desktop videoconferencing systems support document sharing and multi-point calling.

Dialing in: Each site initiates the video call by dialing into the bridge.

Dialing out: VSGi initiates the video call by dialing each site participating in the videoconference.

Document camera: A specialized camera used for taking pictures of still images (pictures, graphics, text pages) to be sent as part of a videoconference.

Document sharing: A feature supported by many desktop videoconferencing systems that allow participants at both ends of a videoconference to view and edit the same computer document.

Digital signals: Audio/video signals represented by discrete variations (in voltage, frequency, amplitude, location, etc.). A digital clock, for example, displays the time as discrete numeric values rather than angular displacement of analog hands. In general, digital signals can be transmitted faster and more accurately than analog signals. As an example, music from digital compact discs is usually clearer than music from analog records. (Contrast with analog signals.)


Echo-cancellation: Process of eliminating acoustic echo in a audio speaker phone, voice conference phone, videoconferencing room.

Encryption: Encryption is a way of scrambling data so that only those who know how to unscramble the data get access to it. With encryption, you can rest assured that all your video communication is private. Embedded encryption allows you to enjoy the full array of features without any degradation in performance, unlike third-party, non-embedded encryption solutions. All encryption methods use common algorithms.


FCIF/QCIF: Standards-based formats for communicating between videoconferencing systems from different vendors. QCIF is one quarter of the resolution of FCIF.

Frame rate: Frequency in which video frames are displayed on a monitor, typically described in frames-per-second (fps). Higher frame rates improve the appearance of video motion. Broadcast TV (full motion video) is 30 frames-per-second.

Full duplex audio: Two-way audio simultaneously transmitted and received without any interference or "clipping." A common feature of room-based videoconferencing systems. Contrast with half duplex audio.

Full motion video: Full motion video is equivalent to broadcast television video with a frame rate of 30 fps. Images are sent in real time and motion is continuous.


H.320 standard: A widely used video compression standard that allows a wide variety of videoconferencing systems to communicate.

H.323 standard: A new standard providing a foundation for audio, video, and data communications across IP-based networks, including the internet.  By complying with H.323, multimedia products and applications from various vendors can inter-operate, allowing users to communicate without concern for compatibility.

Half duplex audio: Two-way audio transmitted and received in turn (rather than simultaneously) so only one site can speak at a time. Contrast with full duplex audio.

HD: High Definition. Learn more about HD videoconferencing.

HDTV: High Definition Television. Term widely used in the use, and broadcast method, of flat-panel displays such as, LCDs and plasma screens.


IP: Internet Protocol. A protocol that specifies the way data is broken into packets and the way those packets are addressed for transmission. IPv4 is the version in widespread use and IPv6 is the next generation and most likely candidate to replace the current protocol.

ISDN: Integrated Services Digital Network. ISDN is essentially a digital network that will provide seamless communication of voice, video, and data between individual desktop videoconferencing systems and group videoconferencing systems. There are two types of ISDN lines: BRI or PRI.


Kbps: Kilobits per second. A unit of measurement used to calculate the speed of transmission.  The higher the Kbps or speed, the better the quality of the voice or video conference.


Multipoint videoconference: Videoconference with more than two sites. The sites must connect via a video bridge or multipoint control unit (MCU). (Compare with point-to-point videoconference.)

MCU: Multipoint Control Unit. An MCU facilitates or "bridges" the communication of three or more audio and/or video sites in a videoconference.

MPLS: Multiprotocol Label Switching. MPLS is the most advanced mechanism used to control traffic routing and consistency of throughput within Service Provider backbone networks.  Relative to the transport of real-time videoconferencing, MPLS offers two powerful benefits:

  • The ability to prioritize video transport above other traffic types thereby guaranteeing consistent video throughput  (VSGi’s vIPConnect network service  guarantees 100% throughput for video-- at all time and under all network conditions)
  • The ability to move video traffic on predetermined route paths through the network with performance parameters engineered specifically for video (VSGi’s vIPConnect network service  guarantees 100% in-sequence packet delivery with latency variation or “jitter” less than 5ms-- at all time and under all network conditions)

Narrowband: A low-capacity communications circuit/path. It usually implies a speed of 56Kbps or less. (Contrast with wideband and broadband.)

NTSC: Standard for scanning television signals. Used in the U.S., Canada, and Japan.


PAL: Standard for scanning television signals. Used in most European countries.

Point-to-point videoconferencing: Videoconference between two sites. (Compare with multipoint videoconference.)

PRI: Primary Rate Interface (ISDN). A PRI consists of 23 B-channels and one D-channel (U.S.) or 30 B-channels and one D-channel (Europe). The bandwidth is measured in 1.54 Mbps (Megabits per second).

Proprietary compression algorithm: A vendor-specific algorithm for compression of a video signal. A videoconferencing system using a proprietary algorithm can only communicate with a remote site using the same algorithm. Many vendors also adhere to standard compression algorithms to facilitate communication across platforms.

Protocol:  Defines the type of system the client is utilizing, including: H.320 – universal algorithm· Continuous presence- Speed – the rate (and ultimately the number of lines) a conference uses.  The more lines, the higher the speed and better picture quality.

PSTN (or POTS): Public Switched Telephone Network. The collection of interconnected systems operated by the various telephone companies and administrations (telcos and PTTs) around the world. Also known as the Plain Old Telephone System (POTS) in contrast to VoIP and ISDN.


Room-based videoconferencing: Videoconferencing using a sophisticated system. Appropriate for large groups.  (Compare to desktop videoconferencing.)


Speed matching: Upgrades the speed of a lower channel codec to a higher channel conference.

Standard compression algorithm: An algorithm convention for compression of a video signal. Adherence to standards allows communication among a wide variety of videoconferencing systems, though not with the same clarity as two similar systems using a proprietary algorithm. H.320 is the most widely accepted standard in use today.


T1: A T1 circuit, equal to 1.54 Mbps, is a bandwidth speed used when speaking in terms of Internet Protocol (IP) communications. Also see PRI for ISDN communications network bandwidth at the same speed.


Video bridge: Computerized switching system that allows multipoint videoconferencing. See MCU

Videoconferencing: Communication across long distances with video and audio contact that may also include graphics and data exchange.

Video streaming: Streaming is a server/client technology that allows live or pre-recorded data to be broadcast in “real time,” opening up the network for traditional multimedia applications such as news, training, entertainment, advertising, and a host of other uses.  Streaming enables the internet or company intranet to act as a broadcast medium for audio and video.

Voice-activated videoconference: Refers to a type of videoconference in which the cameras are (1) activated by sound, (2) switch to the site where the sound is originating, (3) display that site on participant monitors.

VoIP: Voice over Internet Protocol or Voice over IP. A protocol for transmitting the human voice in digital form over the Internet or other networks as an audio stream, instead of using traditional telephone lines (PSTN or POTS ). VoIP uses the Internet Protocol (IP), but is not limited to communication by computer—even phone-to-phone communication can be conducted using this technology. Learn more about VoIP phones.


Wideband: A medium-capacity communications circuit/path. It usually implies a speed from 64Kbps to 1.544Mbps. (Contrast with broadband and narrowband.)


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