| Term |
Definition |
| D Channel |
In Integrated Digital Service Network Technology a channel outside of the normal information transfer bandwidth used for the transmission of control signals. |
| D/A |
Digital to Analog. |
| D4 |
In T1 digital transmission technology a "fourth generation" channel bank. A channel bank is the interface between the T1 carrier system and a premises device such as a PBX. |
| DAA |
Data Access Arrangement. |
| DAB |
Digital Audio Broadcasting. |
| DAC |
Digital to Analog Converter. |
| DACC |
Digital Access Station. |
| DACS |
A time-slot switch which allows T1 or E1 lines to be remapped electronically at the DS-0 (64 kbps) level. Also called DCS or DXS. |
| DAL |
Data Access Lines. |
| DAM |
DECT Authentication Module. |
| D-AMPS |
Digital Analog Mobile Phone system. |
| DAQ |
Data AcQuisition. |
| Dark Fiber |
Unused fiber; a fiber carrying no light. |
| DAS |
Dual Attachment Station - An FDDI station that offers two connections to the FDDI network, and which is capable of serving the dual (counter rotating) ring. |
| Data Access Arrangement |
A Central office interface circuit with re-duced functionality. |
| Data Communications |
The movement of data by means of electrical (or photon in the case of fiber optics) transmission systems. |
| Data Compression |
The generic term for any one of a number of techniques used to reduce the number of bits transferred in unit time without modifying the informational content of a message. |
| Datagram |
A logical entity containing an IP header and the IP message contained within. IP protocols communicate through datagrams, but these are sometimes fragmented on links. Datagrams are sent as packets on the link layer, and a datagram may be sent as one or many packets. |
| Data Grade |
A term used for twisted-pair cable used in networks to carry data signals. Data grade media has a higher frequency rating than voice grade media used in telephone wiring. |
| Data Link |
Any serial data communications transmission path between two devices. |
| Data Network |
Any network of interconnected devices constructed for, and used for, the transfer of data between the devices. |
| Data Network Identification Code |
A four digit number assigned to and used (to specify services) by public data networks. |
| Data Over Voice Frequency |
The frequency used to transmit data on the same transmission line as a voice. Standards are not currently finalized but a typical system uses (mark) 40 kilohertz and (space) 36 kilohertz. |
| Data Over Voice Transmission (DOV) |
A method which allows data and voice to be transmitted at the same time on the same conductor. The data is transmitted by modulating a carrier whose frequency is well above the audio range ( Voice signals are limited to 0-4 Khz by the transmitting equipment). |
| Data PBX |
A PBX which has been designed specifically to switch data sources. May also be referred to as an active star Controller. |
| Data Rate |
A measure of transmission speed. Normally specified in bits per second. |
| Data Stream |
The flow of individual data bits being transmitted through a communications channel to accomplish the transfer of information. |
| Data Switching Exchange |
The equipment installed at a single location to provide circuit switching, packet switching or both. |
| Data Transfer Rate |
The average flow per unit time of information from source to destination. The rate may be measured in terms of bits, bytes, blocks, frames, packets, etc., per second, minute, hour, etc. |
| Data Transparency |
A facility provide by the data link control protocol which allows any pattern of bits, bytes, or characters to appear within the information field of a transmission frame and ensures that NO pattern in this field will be mistakenly treated as control information by the receiver. |
| DAVIC |
Digital Audiovisual Council. DAVIC, now defunct, was established in 1994 with the aim of promoting the success of interactive digital audio-visual applications and services by promulgating Specifications of open interfaces and protocols that maximise interoperability, not only across geographical boundaries but also across diverse applications, services and industries. |
| DAVID |
Digital Audio Video Interactive Decoder. |
| dB |
Abbreviation for decibel. The decibel is the standard unit of measure for expressing the amount of signal power gained or lost in the course of a transmission. |
| dBK |
Decibels - referred to 1 Kilowatt. |
| dBm |
Power in dB relative to 1 mW. |
| dBV |
Decibels - Voltage. |
| DC |
i. Direct Conversion, ii. Data Conversion. |
| DC Signaling |
Refers to a variety of techniques for transmitting signaling information using direct current over metallic circuits, for example, loop reverse battery, loop start or duplex signaling. DC signaling is a subset of out-of-band signaling. |
| DCS |
i. Distributed Control System, ii. Data Carrier System, iii. Digital Cellular System. |
| DDA |
Digital Differential Analyzer. |
| DDD |
Direct Distance Dialling. |
| Decimation Filter |
A decimation filter is a lowpass filter designed to provide decimation without the aliasing artifacts associated with simply throwing data away. |
| Decoder |
A device that modifies transmitted information allowing the receiver to understand the information. |
| Decoding |
A process in which one of a set of reconstructed analog samples is generated from the digital character signal representing a sample. |
| DECT |
Digital Enhanced Cordless Telecommunications. |
| Dedicated Line |
A common carrier line which is reserved for the exclusive use of a predefined entity. Is also used to define any type of communications channel which is pre-assigned to a specific user. |
| Delay Distortion |
The distortion of an analog signal as it passes through a transmission medium which is the result of the fact that different frequencies travel through the medium at slightly different speeds. |
| Delta Modulation |
A single bit per sample iterative coding technique for converting an analog signal to a digital bit stream which can be decoded simply by integrating the digital bit stream and low pass filtering. To obtain telephony quality transmission requires a sample rate of approximately 8kHz. |
| Delta-Sigma Modulation |
A single bit per sample iterative coding technique for converting an analog signal to a digital bit stream. The resulting bit stream is a pulse density function of the original analog signal which can be re-covered simply by low pass filtering the bit stream. To obtain telephony quality transmission requires a sample rate of approximately 8kHz. |
| Demultiplexer |
A device which separates the individual signals (from individual devices) which have been multiplexed onto a high speed transmission system. |
| Demux |
Demultiplexer. |
| Differential Gain |
Differential gain is how much the color saturation changes when the luma level changes (it isn't supposed to). For a video system, the better the differential gain -- that is, the smaller the number specified -- the better the system is at figuring out the correct color. |
| Differential Phase |
Differential phase is how much the hue changes when the luma level changes (it isn't supposed to). For a video system, the better the differential phase -- that is, the smaller the number specified -- the better the system is at figuring out the correct color. |
| Differential Pulse Code Modulation |
A form of pulse code modulation where efficiency is enhanced by only transmitting the difference between the current signal strength and the pervious pulse signal strength rather than the absolute values. |
| Differential Transmission |
The process whereby information is carried as the difference in voltage between two transmission lines. |
| Digit Timeslot |
A timeslot allocated to a single digit. |
| Digital 8 |
Digital 8 compresses video using standard DV compression, but records it in a manner that allows it to use standard Hi-8 tape. The result is a DV "box" that can also play standard Hi-8 and 8 mm tapes. On playback, analog tapes are converted to a 25 Mbps compressed signal available via the i-Link digital output interface. Playback from analog tapes has limited video quality. New recordings are digital and identical in performance to DV; audio specs and other data also are the same. |
| Digital Circuit Multiplication |
A method of increasing the capacity of digital voice channels |
| Digital Composite Video |
Digital video that is essentially the digitized waveform of NTSC or PAL video signals, with specific digital values assigned to the sync, blank, and white levels. |
| Digital Loopback |
A technique used to isolate faults in the digital circuitry of a transmission system. |
| Digital Network |
A network consisting of transmission and switching equipment capable of interconnecting digital circuits and requiring timing reference to avoid slip impairment. |
| Digital pulse wireless |
Also known as Ultra wideband radio - a wireless technology for transmitting large amounts of digital data over a wide spectrum of frequency bands with very low power. Ultra wideband radio not only can carry a huge amount of data over a short distance (up to 230 feet) at very low power (less than 0.5 milliwatts), but has the ability to carry signals through doors and other obstacles that tend to reflect signals at more limited bandwidths and a higher power. Ultra wideband radio can be compared with another short-distance wireless technology, Bluetooth, which is a proposed standard for connecting handheld wireless devices with other similar devices and with desktop computers. |
| Digital Signal Cross-Connect (DSX) |
A facility for circuit re-arrangements, patching and testing purposes. the DSX is designated DSX-N, where N indicates the hierarchy of the digital network interconnected at that point. |
| Digital Signaling |
A form of Signaling whereby information is represented in the form of discrete (on/off, high/low) signals. |
| Digital Speech Interpolation |
A voice compression technique which takes advantage of the natural pauses in human speech to multiplex other conversations onto the same transmission medium. |
| Digital Television (DTV) |
Refers to all formats of digital television, including high definition television (HDTV), and standard definition television (SDTV). Also referred to as ATV (advanced TV). |
| Digital Transmission Content Protection |
An encryption method (also known as "5C") developed by Sony, Hitachi, Intel, Matsushita and Toshiba for IEEE 1394 interfaces. |
| Digital Vertical Interval Timecode |
DVITC digitizes the analog VITC waveform to generate 8-bit values. This allows the VITC to be used with digital video systems. For 525-line video systems, it is defined by SMPTE 266M. BT.1366 defines how to transfer VITC and LTC as ancillary data in digital component interfaces. |
| Direct Broadcast Satellite (DBS) |
A broadcast technology that uses satellites orbiting the Earth to broadcast television or data signals to an 18" dish antenna. |
| Discrete multi-tone modulation (DMT) |
A method of transmitting data on copper phone wires that divides the available frequency range into 256 sub-channels or tones, and which is used for some types of DSL. |
| Distributed PBX |
A private branch exchange (PBX) system whose component parts are located throughout an organization and interconnected using a local area network. |
| Distribution Frame |
The wall mounted frame used to terminate and cross connect telephone circuits. |
| DLS |
Digital Subscriber Lines. |
| DMOS |
Double-diffused Metal Oxide Semiconductor. |
| Dolby Digital |
An audio compression technique developed by Dolby. It is a multi-channel surround sound format used in DVD and HDTV. |
| Double Buffering |
As the name implies, you are using two buffers - for video, this means two frame buffers. While buffer 1 is being read, buffer 2 is being written to. When finished, buffer 2 is read out while buffer 1 is being written to. |
| Downconverter |
A circuit used to change a high-frequency signal to a lower frequency. |
| Downstream |
Data direction that moves away from a central distribution point and toward a user. Faster than upstream (user to network) rate. |
| DPCM |
Differential Pulse Code Modulation. |
| DPSK |
Differential Phase Shift Keying. |
| DRAM |
Dynamic Random Access Memory. |
| Drop-out |
A short period of time during which a transmission service looses the ability to transmit data. |
| DS3 |
Digital Signal level 3. A North American digital hierarchy signalling standard for transmission at 44.736Mbit/s |
| DSA |
Digital Signal Algorithm. |
| DSK |
Downstream Keying |
| DSL |
Digital Subscriber Line; technology that provides high-speed dedicated access to the Internet. Combines two-way voice and data transmissions at very high speeds over existing telephone lines. |
| DSLAM |
Digital Subscriber Loop Access Multiplexer. A network device designed to multiplex many individual DSL circuits into a single high speed circuit, generally ATM to an ISP. |
| DSP |
Digital Signal Processor (or Processing). |
| DTMF |
Dual-Tone Multi Frequency - Standard for touch tones telephones. |
| DTS |
Digital Theater Systems. It is a multi-channel surround sound format, similar to Dolby Digital. For DVDs that use DTS audio, the DVD - Video specification still requires that PCM or Dolby Digital audio still be present. In this situation, only two channels of Dolby Digital audio may be present (due to bandwidth limitations). |
| DTV |
Digital Television. |
| Duplex |
Simultaneous transmission in both directions, sometimes referred to as full duplex to differentiate it from half duplex, which is alternating transmission in each direction. Transmission in only one direction is called simplex transmission. |
| DUV |
Data Under Voice. |
| DVB |
Digital Video Broadcasting. |
| DVB-C |
DVB digital cable delivery system. Digital cable system that is compatible with DVB-S. |
| DVBIRD |
Digital Video Broadcasting Integrated Receiver/Decoder |
| DVD |
Digital Versatile Disc. |
| DWMT |
Discrete wavelet multitone. |
| DXI |
Data Exchange Interface - Protocols used between routers and DSUs for SMDS and ATM. |
| Dynamic Bandwidth Allocation |
A technique used to allocate transmission channels ONLY to devices which are transmitting. Used in some T1 Multiplexer devices. |
| Dynamic Range |
The dynamic range of a system is a meas-ure of its ability to handle a wide range of input amplitude and is defined as the ratio of the largest resolvable signal to the smallest signal that can be handled. |
| Dynamic routing |
A switching and routing technique which can be (or will) change as conditions in a network change. |
