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Face-to-face contact (FTFC): Describes meetings where all participants are physically present at the same location. Commonly used as a point of comparison for the various media of teleconferencing.
Feedback: a. Video: Distortion of the picture caused when a video signal re-enters the switcher and becomes overamplified. b. Audio: Unpleasant howl from loudspeaker caused when the loudspeaker sound inadvertently is fed into the microphone and subsequently overamplified.
Field: One-half of a video frame. One field of a video frame contains the even-numbered scan lines; the other contains the odd-numbered lines. In full motion video, one field is transmitted every 1/60 of a second.
Field storage: A device that stores a single field of video information.
FOMA: A mobile telephone service introduced in Japan in 2002 by NTT’s DoCoMo called Freedom of Mobile Multimedia Access. FOMA allows for the transmission of still video as well as motion video, using the new third-generation mobile telephone transmission service commonly called 3G. The new FOMA phones even allow for the transmission of near-CD quality music over mobile telephones. NTT is running trials of two-way interactive videoconferencing over the new 3G FOMA mobile telephones.
Footprint: 1. The geographic region on the earth that can easily receive and interpret a signal broadcast from a communications satellite. 2. The surface area on a floor, desk, or tabletop required to accommodate a piece of equipment.
Four-wire circuit: A circuit that contains two channels, one designated as a transmission channel, and the other as a receive channel. Named a four-wire circuit because four physical wires are generally used in pairs to complete the circuit.
Frame: A complete video image, consisting of two fields. Each NTSC frame is made up of 525 scan lines, half of which are allocated to each field. For full motion video, frames are transmitted at the rate of 30 per second. The European PAL standard dictates frames of 625 scan lines sent at the rate of 25 per second. The SECAM standard also requires 625-line frames.
Frame storage: A device that stores a full frame, or two fields, of video information.
Frequency division multiple access (FDMA): A method of enabling several communications devices to use the same transmission channel by allocating a portion of the capacity of the channel on a pair-by-pair basis using frequency division multiplexing (FDM).
Frequency division multiplex (FDM): A modulation technique that divides the total capacity of a communication medium into channels, with each channel assigned a specific frequency band.
Frequency spectrum: The full range of frequencies.
Full duplex: Sending data in both directions at the same time. Usually higher quality, but requires more bandwidth. In videoconferencing, full duplex will result in a more natural image. [Source: York Telecom]
Full duplex audio: See Duplex audio.
Full motion video: Continuous motion, often color, video used in teleconferencing. Often similar to the quality on commercial television (referred to as broadcast quality).
Fully automated: A conference call where most, if not all, features are automated. Such calls do not require an operator, though in many cases an operator can be added by pressing the "0" in the telephone keypad. With fully automated calls, most of the features, such as announcing a person coming onto the call, and adding or dropping callers from the conference call, are managed by the call moderator through the use of codes entered via a telephone keypad. Often callers are required to key in a personal identification number (PIN—also called a passcode) on their phone before they are allowed on the conference call, as a way of offering security. Some fully automated calls can be managed through a Web interface, and even reserved through a Web interface, although most fully automated calls are not reserved, and are therefore also called reservationless calls.
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G.723.1: A standard recommended by the ITU in 1995 that described a way of digitally coding voice, for communications over a packet network. While the standard was designed for use over private packet networks, it was first used for communications over the public Internet relying on the Internet Protocol (IP), for which it was not designed. G.723.1 is part of H.323.
Gatekeeper: Used in H.323 solutions, the gatekeeper provides several important functions. First, it controls access to the network, allowing or denying calls and controlling the bandwidth of a call. Second, it helps with address resolution, making possible email type names for end users, and converting those into the appropriate network addresses. They can also handle call tracking and billing, call signaling, as well as the management of gateways. [Source: York Telecom]
Gateway: Gateways provide a link between the H.323 world and other video conferencing systems such as one using ISDN-based technology. [Source: York Telecom]
Geosynchronous (geostationary) orbit: An orbit located 22,300 miles above the earth’s equator. This orbit allows communications satellites to remain stationary above the intersection of a longitude with the equator on the earth. Because of this, earth stations can be permanently pointed at one location in the sky to continually transmit and receive information from a satellite.
Gigahertz: One billion cycles per second. Abbreviated gHz.
Graphics tablet: See Electronic tablet.
Gray scale: The ability to render properly the various brightness levels in a reproduced image. For a digitized signal, broadcast-quality gray scale is considered to be at least 256 shades of gray, which can be coded in an 8-bit picture element.
Group videoconferencing system: These systems are traditionally designed for conference rooms that support 5-12 participants. They contain multiple monitors with full-function codecs. They can be conveniently moved between multiple locations or remain stationary in one room. They also have the flexibility to add peripherals to the base system. [Source: York Telecom]
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H.320: Videoconferencing standard that includes a number of individual recommendations for coding, framing, signaling and establishing connections. This commonly used standard describes how to transmit voice and video data over ISDN and fractional T1 lines. [Source: York Telecom]
H.323: Videoconferencing standard ratified in 1996, which describes how to transmit voice and video data over the local area and wide area networks using TCP/IP as the transmission protocol. H.323 has the promise to significantly reduce the cost of desktop video connections and enable videoconferencing to become another LAN application. [Source: York Telecom]
Hands-free telephone: A telephone device with an amplifier that allows the user to dial without removing the handset, and/or to hold telephone conversations without using a handset. Generally relies upon condenser microphones embedded in the telephone instrument and operates as a loudspeaking telephone.
Hertz: (Named after Heinrich Rudolph Hertz, a German physicist.) A measure of frequency, one cycle or complete oscillation of a radio waveform per second.
High Order Differential Pulse Code Modulation (HO-DPCM): A form of DPCM used by picture processors that not only uses adjacent points on a line, but adjacent lines as well. DPCM is a one-dimensional form of intraframe coding. HO-DPCM is a two-dimensional form.
HO-DPCM: See High Order Differential Pulse Code Modulation (above).
Hybrid meeting: A meeting that consists of a mix of conference users; i.e., video, audio or document. [Source: Global Crossing]
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iMode: A mobile telephone system available in Japan from NTT’s DoCoMo subsidiary. Phones using iMode have the ability to transmit and read e-mails, transmit short text messages using SMS (Short Message Service), and to use services that rely on graphics, most often video game playing.
Interactive audio: An audio conferencing system, used alone or in conjunction with other media such as audiographics or full motion video, that allows all sites participating to hear all comments made by others, and to be heard in turn by them. Some interactive audio systems allow participants to interrupt each other and/or to speak simultaneously from the various sites participating. This is often referred to as full duplex or open audio.
Interactive communication: Communication that goes both ways. All teleconferencing is, by definition, interactive. Some "teleconferences" use one way video and one way audio.
Interactive voice response (IVR): Use of DTMF signals to interact with a computerized data collection or information system.
Interface: An electronic device that allows dissimilar components in a system to communicate.
Interference: In a teleconferencing system, the inclusion of unwanted signal information in a channel of desired communications information. Interference is what occurs when music from a radio station can be heard while listening to another radio station on a car radio. I.e., noise.
Interframe coding: A process used by some picture processors (codecs) that relies upon the difference between two successive video frames. See High Order Differential Pulse Code Modulation, Conditional replenishment, Motion compensation coding.
Internet Protocol voice telephones: Voice telephones that are designed to communicate over packet networks, often over the Internet using Internet Protocol (IP). Also known as voice over IP (VoIP) telephones.
Interoperability: The ability of electronic components produced by different manufacturers to communicate across product lines. [Source: York Telecom]
Intraframe coding: A method used by some picture processors (codecs) that relies upon information completely contained within a single frame of video information. See Cosine transform coding, Scene adaptive coding.
IP: Internet Protocol. IP was developed by the government for use in internetworking multiple computer networks. [Source: York Telecom] IP specifies the formatting and addressing of packets for transfer over the Internet.
Investor Relations calls: Conference calls where publicly traded companies disclose information to financial analysts, the press, and their shareholders. Also known as earnings calls or IR calls.
IP phones: See Internet Protocol voice telephones (above).
IP speakerphones: Speakerphones that rely on IP or VoIP communications. See Internet protocol voice telephones (above).
IR calls: See Investor Relations calls (above).
ISDN: Integrated Services Digital Network. A set of protocols and interface standards that effectively constitutes an integrated telephone network. ISDN can transmit digital data as well as voice without a modem. [Source: York Telecom]
IVR: See Interactive voice response.
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Jitter: A signal timing error that results in distortion of the received signal. In Internet terms, jitter is the measure of latency of individual packets in a message or stream.
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kbps: Also kb/s. See Kilobits per second (below).
kHz: See Kilohertz (below).
Kilobits per second: A data rate of one thousand bits of information per second.
Kilobyte: One thousand bytes or “characters” of digital information, consisting of from six to eight bits. In reality, 1024 bytes of information.
Kilohertz: One thousand Hertz or cycles per second, abbreviated kHz.
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LAN: See Local area network.
Land lines: A portion of a terrestrially based transmission system that uses either copper wire or coaxial cable.
“Last mile” services: Transmission services that link a customer’s premises with a common carrier’s transmission node. Usually used to describe land line or microwave links tying a customer’s premises to a broadband or high data rate transmission system such as a satellite uplink.
Latency: The length of time it takes a packet to move from source to destination; delay. [Source: York Telecom]
Leased line: A dedicated circuit typically provided by a telephone company. [Source: York Telecom]
Line-of-sight: A transmission path uninhibited by physical objects in the intervening terrain. Line-of-sight distances vary depending upon the strength of the signal transmitted between transmitters and receivers used and the relative vertical distance between the transmitter and the receiver. The ultimate limitation on line-of-sight is the curvature of the earth.
Local area conferencing: Used to describe teleconferencing systems tying together groups in a single city or metropolitan area.
Local area network (LAN): A communications network, usually used for data, but sometimes also accommodating voice and video, that links a small area, such as a building or an industrial park. Most LANs have a maximum link length of less than a mile; most are based on coaxial cable.
Loudspeaking telephone: A hands-free or amplified telephone that incorporates a microphone and speaker, allowing up to approximately three individuals in an office to participate in a teleconference. A good example of a loudspeaking telephone is the speakerphone. Loudspeaking telephones are adjuncts or add-ons to normal telephones, as they do not have their own dialing capability.
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