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| Analog, IP, Video Phones, Cameras, Video Conference & Video Surveillance Products |
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ADSL (Asymmetrical Digital Subscriber Lines) A communications technology used to transmit high-speed digital data over existing copper POTS telephone lines. It is expected to transmit up to six megabits per second and be used for video-on-demand services to telephone company customers Algorithm - A set of specifications that define methods and procedures for transmitting audio, video, and data. Algorithms are fundamental to image compression (motion and still), because they allow an information-intensive file or transmission to be squeezed to a more economical size. Analog - Continuously varying representations of numerical values by physical variables such as voltage and amplitude. Depending on the precision with which they are sampled/measured , they can vary infinitely. Each sample can produce a value that corresponds to the unique magnitude of the variable. Analog Gateway - A means of connecting dissimilar codecs. Incoming digital signal from one type of codec is decoded by a similar codec and converted to analog. The Analog signal is then passed to the dissimilar codec, coded, and decoded at the far end. Analog gateways achieved interoperability in a nonstandard environment, but have the disadvantages of degrading video and audio quality and often reducing functionality. Annex D Graphics - An addendum to the H.320 videoconferencing protocol used for still image transfer between dissimilar videoconferencing systems. Audio - The term is used in video communications to describe electrical signals that carry sounds. It also describes sound recording and transmission systems. B Channel - The ISDN circuit-switched bearer channels, capable of transmitting 64Kbps of digital information. Bandwidth - Amount of information transmission capacity. In analog systems it is measured in hertz, as the difference between the highest and lowest frequencies a channel can carry. In digital systems the bandwidth is measured in bits per second. BRI (Basic Rate Interface) - An ISDN access or subscriber line, consisting of two 64Kbps B ("bearer") channels and one 16Kbps D channel used for both data and signaling purposes. The ISDN Basic Rate Interface, or BRI, provides two B channels and one 16 Kbps D channel (2B+D) for a total of 144 Kbps. (128K for Video) Broadcast - One-way video, usually from a single transmitting site to many receiving sites. In some cases, the receiving sites can communicate to the transmitting site on an audio-only basis. Broadcast Quality - Used to describe an audiovisual signal that delivers quality that is approximately as good as television. CCITT - International Telephone and Telegraph Consultative Committee. Now known as ITU-T. An international body that sets worldwide telecommunications standards, such as the Px64 standard for videoconferencing. CCD - Charge coupled device used in cameras. It consists of a shift register that stores samples of analog signals. Camera - An electronic device used to convert visual images into electrical impulses. It scans an image and describes the light that is present using an optical system and light-sensitive pick-up tube. Channel Bank - Used to divide a T1 access facility into 24 digital or analog circuits. CIF (Common Intermediate Format) - Part of the ITU-T's H.261 and H.263 standards. The 288 luminance lines contain 352 pixels and 144 chrominance lines contain 176 pixels. CIF is sent at frame rates of 7.5, 10, 15 or 30 per second. Codec - Coder-Decoder: a device that encodes an incoming analog signal into a digital signal for transmission to another codec. The digital signal is decoded into analog format. In videoconferencing, codec typically code and decode video and audio. Compression - Reduction of the amount of information to accommodate cost-effective digital transmission to another codec. For example, sub-T1 video codecs compress analog signals (roughly equivalent to 90,000 kilobits per second) to digital rates varying from 56 to 1,544 kilobits per second. POTS-based video compression can transmit at 33.6 kilobits per second or lower. Compression Ratio - A compression ratio, usually expressed as 5:1, refers to the size of the original data versus the size after compression. If data has been reduced to one-fifth the original size, the compression ratio is 5:1. Data Conferencing - Enables people in different locations to work on the same document via networked computers. Also referred to as collaborative computing Dedicated Line - A permanently assigned path connecting geographically dispersed sites on a long distance network. Synonym: private line: leased line. Delay - Refers to the slight delay that sometimes occurs when transferring video, data and audio signals. DES - Digital Encryption Standard, an encryption method defined by the National Bureau of Standards. Desktop Video - Communications that rely on videophones or personal computers that offer a video window. DHCP - Dynamic Host Configuration Protocol. DHCP servers permit multiple devices to share a group of IP addresses, assigning one to a specific device as needed. Digital - Information contained in the form of 0s and 1s for transmission on digital media, including fiber, microwave, and satellite. Digital information may include video, audio, graphics, and data. Digital Service Unit (DSU) - A type of customer premises equipment that terminates a single DSO or fractional T1. Distance Learning - The incorporation of video and audio technologies (usually interactive) into the educational process so that students can attend classes and training sessions from remote locations. DSO - Digital Signal level zero. One 56Kbps (or 64Kbps) line or circuit. DS1 - Digital Signal level one. One 1.544Mbps digital signal comprised of 24 lines or channels, each with 64 Kbps capacity (see T1). Digital Switch - A means of supporting multiway conferencing using the signals in their digital format without converting them to analog. Digital switches permit multiple users with similar codecs to conference generally with voice-activated switching. Document Camera - A specialized camera which is mounted on an adjustable neck for taking pictures of still images- pictures, graphics, etc.- for use in a videoconference. Dual 56 - Combination of two 56Kbps lines for a 112Kbps video transmission capacity. Dual 56 typically allows direct dialing of a videoconference call. Echo Cancellation - A mathematical process that predicts an echo and removes that portion of the signal from an audio waveform to eliminate acoustical echo. Encryption - Alteration of transmitting information to protect it from unauthorized tapping. ESS - Electronic Switching System, "class five" switch or 5ESS is the most common CO in the US. FCIF or (CIF) - Full Common Intermediate Format. A video resolution of 352 pixels horizontally and 288 pixels vertically. It is used primarily in higher bit rate (128Kbps and higher) video conferencing. Firewall - A network node set up as a boundary to prevent traffic from one segment to cross over into another. Flash Memory - Memory which occupies little space and does not need continuous power to be retained. F.R.A.D. - Frame Relay Access Device: F.R.A.D. takes the information streams and multiplexes them on public or private frame relay networks. Frame Relay - A high-speed packet switching protocol used for wide area networks (WANs). It is faster than traditional X.25 networks, because it was designed for today's reliable circuits and performs less rigorous error detection. It provides for a granular service up to DS1 rates of 1.544 Mbps and is suited for data and image transfer. Because of its variable-length packet architecture, it is not the most efficient technology for real-time voice and video. Frames Per Second (fps) - Frequency with which video frames appear on a monitor. Broadcast-quality video generally consists of 30 frames per second. Full-motion videoconferencing typically offers video in the range of 10 - 15 frames per second. At very low bandwidths, such as 56 or 112 Kbps, the frame rate may be lower. Freeze Frame (Still Video) - A single frame displayed motionless on a screen. When freeze frame video is viewed , the viewer sees successive images refreshing a scene but lacks a sense of continuous motion. Full-Duplex Audio -Audio that allows local and remote conference participants to speak simultaneously with out losing audio contact. Full-duplex audio may be provided in a point-to-point or multipoint conference. Full-Motion - In compressed video, picture quality that is generally acceptable to users although not of broadcast quality. Typically full-motion compressed video provides anywhere from 10 - 30 frames per second depending on the bandwidth allocated. Graphics - Transmission of still images, usually from a video source, but in some cases PC-generated. GUI - (Graphical User Interface) A graphics-based user interface that incorporates icons, pull-down menus and a mouse. The GUI has become the standard way users interact with a computer. The three major GUIs are Windows, Macintosh and Motif. In a client/server environment, the GUI resides in the user's client machine. G.711 - 3KHz audio-coding at 64Kbps. G.722 - 7KHz audio-coding at 64Kbps. G.728 - 3KHz audio compression at 16Kbps (wideband audio). Half-Duplex Audio - Audio that permits only one site to speak at a time. H.221 - The ITU-T standard relating to communications protocol for videoconferencing. H.223 - Part of the ITU-T's H.324 standard that specifies a control/multiplexing protocol. H.231 - Multipoint for linking three or more H.320 codecs. H.261 - The ITU-T Px64 standard relating to the video compression algorithm. H.230 - The ITU-T standard that defines call control and indication. H.242 - Call set-up and disconnect of two point videoconferencing. H.233 - Encryption. H.243 - Defines call control procedures between H.231 MCU and H.320 codecs. H.263 - Refers to the compression techniques for low data rate transmission used in H.324 video. A more sophisticated codec than H.261 which uses half-pixel increments. H.320 - ITU-T standard which defines multimedia systems for communication on switched networks for point-to-point or multi-point conferences. H.323 - ITU-T standard which defines multimedia systems for communication on packet based networks (IP Networks) H.324 - ITU-T standard which defines multimedia systems for communication on the public switched telephone network (Plain Old Telephones or POTS). Narrow bandwidth transmission. Handshake - In video communications , it is the process in which codecs interoperate using a common algorithm. IEEE - (Institute of Electrical and Electronic Engineers) A membership organization that includes engineers, scientists and students in electronics and allied fields. Founded in 1963, it has over 300,000 members and is involved with setting standards for computers and communications. IETF - Internet Engineering Task Force . A working group within the Internet. The IETF works on the specifications of new standards. In-band - Transmission taking place within allocated bandwidth. For example, a video call with total of 384Kbps may allocate 64 Kbps for audio, leaving 320Kbps for video. Integrated Presentation System - Presentations such as those created in Microsoft® PowerPoint®, can be displayed and presented to the far site while simultaneously being presented to remote users connected via the Internet/Intranet. Interactive - Communication in which all participating sites have equal capability. Interactive videoconferencing permits all sites to see and hear one another. Interoperability - Communication between dissimilar codecs. The ITU-T Px64 standard is designed to permit interoperability. Intranet - A new network model, based on the idea of making information and communications as accessible on internal corporate networks as it is on the public Internet. A recent poll of 50 Fortune 1000 companies interviewed by Forrester Research obtained these definitions: (1) Web technologies developed for internal use: 30% ; (2) A corporate TCP/IP-based LAN: 26% ; (3) Using an internal Web to communicate with business partners: 6% ; (4) Don't know: 38% Inverse Multiplexer (Imux) - A device that creates a single higher-speed transmission by combining and synchronizing two or more channels. IP - Internet Protocol. ISDN (Integrated Services Digital Networks) - A switched network service providing end-to-end digital connectivity for transmitting voice, data, and video simultaneously over a single line verses multiple. Uses high-speed, out-of-band signaling. There are two major forms of ISDN: BRI and PRI. ISP - (Internet service provider). Currently, there are more than 1,500 ISPs around the world. Beyond providing the network connections, an ISP worth having has to guarantee 7-by-24 service and support. That means constant security monitoring, configuration management, auditing, and load planning. At the high end of the ISP spectrum, they provide end-to-end connectivity and outsourcing services, to calibrate every part of the solution, ranging from the physical plant and telephony services to packet filtering and router configuration. ITU-T - International Telecommunications Union-Telephony Sector. Formerly known as CCITT. An international body that sets worldwide telecommunications standards, such as the Px64 standards for videoconferencing. JPEG - Joint Pictures Experts Group. Still-frame graphics for multimedia. Kilobits per Second (Kbps) - Measure of rate of digital transmission, often abbreviated Kbps. LAN - (Local Area Network) A communications network that serves users within a confined geographical area. It is made up of servers, workstations, a network operating system and a communications link. LEC - Local Exchange Carrier; provides local telecommunications service and access to long distance networks. Local Loop - The communications lines between the long distance subscriber and the LEC switching center. Loopback - A diagnostic test where a signal is transmitted over a communications link or network and then returned to the sending device. Loopbacks are used to make sure the video equipment is working properly and as a way to demonstrate videoconferencing. Lux - A basic unit for measuring light intensity. Luminance and flux. MCU - Multipoint Control Unit, a device that connects multiple sites for audio and video conferencing. Mulitcast - To transmit a message to multiple recipients at the same time. Multicasting is used in teleconferencing and data communications networks. Multicast is a one-to-many transmission that implies sending to several designated recipients, whereas broadcast implies sending to everyone connected to the network. Multiplexer - A device that permits subdivision of a given bandwidth. For example, a T1 Multiplexer may divide a T1 line (1,544Kbps) into two capacities of 768Kbps each. MPEG - Motion Pictures Experts Group: This is a standard for motion video. Multiway - Communication between more than two sites. Multiway communication may occur through a digital switch or through an analog gateway. Multipoint Control Unit - Device which allows more than two sites to be connected in a videoconference. Sometimes called a digital switch or video bridge. Narrowband - Networks designed for voice transmission but can accommodate transmission of low speed data. NT-1 (Network Termination 1) - ISDN device that converts between the U-interface and S/T-interface. NT-1 has a jack for the U-interface from the wall and one or more jacks for the S/T-interface connection to the ISDN videophone or videoconferencing system. Uses an external power supply. NTSC - North American standard for analog video format. National Television Systems Committee. Out of band - Transmission taking place external to allocated bandwidth. A video call with out-of-band audio requires a separate phone line for the audio. PAL - European standard for analog video format. PIP (Picture-in-Picture) - Allows the near-end to view themselves in a small window of the video screen while simultaneously seeing the far end. Pixel - Picture element; a measure of resolution for video format. Primary Rate Interface (PRI) - An ISDN subscriber line consisting of 23 64Kbps B channels and one 64Kbps D channel used for signaling. POP - Point-of-Presence. The location or office where a line from an Inter-Exchange Carrier (IXC) connects to the local telephone company or directly to the user. POTS - Plan Old Telephone System. The analog phone system (including telephones, modems, central offices switches, etc., currently in use around the world. PRI - The ISDN Primary Rate Interface, or PRI, in the U.S. provides 23 B channels and one 64 Kbps D channel (23B+D), equivalent to T1. In Europe, PRI includes 30 B channels and one D channel, which is equivalent to European E1. Proprietary - Systems that use techniques which cannot interoperate with other manufacturer's equipment without a great deal of difficulty. PSTN - Public Switched Telephone Network. Px64 - The ITU-T's international video standard which provides a standard algorithm for video compression and decompression. Formally known as H.261, it was adopted in December 1990. Qos - Quality of Service QCIF - Quarter Common Intermediate Format. A video resolution of ¼ the size of FCIF - 176 pixels horizontally and 144 pixels vertically. It is used primarily ion low bite rate (128Kbps and lower) videoconferencing. RBOC - Regional Bell Operating Company; controls a grouping of local exchange carriers. Resolution - A measure of sharpness or clarity on a monitor. RFC - Request For Comment. An Internet term. The contents of an RFC may range from an official standardized protocol specification to research results or proposals. A set of papers in which the Internet's standards, proposed standards and generally agreed-upon ideas are documented and published. RSVP - Resource Reservation Protocol. An emerging data network standard protocol used to reserve bandwidth within packet networks. It is primarily used in data network routers to guarantee a fixed bandwidth through the router for a single or group of users using real time data (like voice or video). All other traffic not assigned to the reservation (such as e-mail or Web access) is delivered by best effort by the router (as it is today). RS-232 - Connectivity from the codec permitting data inputs for transmission from .3 to 190.2 Kbps. RS-449 - Transmission interface between the codec and the transmission link that typically connects to a t1 Multiplexer. A user RS-449 port may also be available for data transfer. SECAM - French standard for analog video format. SNMP - Simple Network Management Protocol; the protocol governing network management and monitoring of network devices and their functions. SNMP came out of the TCP/IP environment. Standards - Uniform specifications to permit interoperability in videoconferencing. Switched 56 - Transmission network at 56Kbps that allows dial-up videoconferencing. Because picture quality at 56Kbps is often not acceptable, most dial-up videoconferencing takes place on two 56Kbps lines, for a total of 112Kbps (see Dual 56). Telecommunications - The art and science of applying services and technologies in order to communicate over distances. Telecommuting - The process of commuting to work electronically rather than physically. Teleconferencing - The use of telecommunication links to provide audio or audio/video/graphics capabilities. TCP/IP - The international standard protocol used on the Internet and company data networks. It provides worldwide connectivity and includes serves such as the World Wide Web, e-mail, file transfer and remote terminal login. Transmission Speed - Data rate for videoconferencing, usually expressed in Kbps. T1 - Commonly used transmission line for videoconferencing, with a capacity of 1,544Kbps. T.120 - Multilayer protocols for graphics/data transmission. T3 - A 45Mbps leased line. Usually obtained from a local or long distance telephone carrier. U-Interface - Carries the ISDN signals over over a single pair of wires between a subscriber's location and the Central Office. Video - A sequence of still images that, when presented at a sufficient frame rate, give the illusion of fluid motion. Videophones - These products were originally aimed at residential markets. These products are being used in numerous applications as a cost-effective solution. Due to the improvements of codecs an H.324 standard systems can provide video transmission using a 33.6Kbps modem over a POTS network. An H.320 standard unit can transmit between 56Kbps - 128Kbps over an ISDN network. Videoconferencing - Communication across long distances that integrates video, audio and data for contact between sites separated by distance. Voice Activated Switching - In multiway videoconferencing, used so that all participating sites automatically see the site which is currently speaking. Voice-tracking - Camera automatically tracks the voice of the person speaking. V.35 - Transmission interface between the codec and the transmission link that permits Switched 56 connectivity. Web Server - A computer that delivers (serves up) Web pages. Every Web server has an IP address and possibly a domain name. For example, if you enter the URL http://www.sandybay.com/index.html in your browser, this sends a request to the server whose domain name is sandybay.com. The server then fetches the page named index.html and sends it to your browser. Web Browser - A software application used to locate and display Web pages. Three of the most popular browsers are Netscape Navigator, Microsoft Internet Explorer, and Spyglass Mosaic. All of these are graphical browsers, which means that they can display graphics as well as text. In addition, most modern browsers can present multimedia information, including sound and video. Zoom - Applied to cameras; zooming provides the ability to take close-up and distant shots using the same lens. |
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Copyright© Wind Currents, Inc. All Rights Reserved. Last Revised in 2006
