电信专业英英词典D-4（在线收听）

　　D type Channel Bank

　　A D type channel bank is channel termination equipment used for combining (multiplexing) individual analog channel signals on a time division basis. D type channel banks provide interfaces for "n" analog signal inputs. Each analog input signal is directed to a codec for en coding to PCM samples. A part of a Tl carrier system.

　　DACS

　　digital access & cross-connect system

　　DARPA

　　Defense Advanced Research Projects Agency

　　Data Compression

　　Data compression is a technique that removes redundancy in transmitted bit patterns to reduce transmission rates by 20% to 200%. For example, a modem designed to send and receive data at 1200 bps without data compression may be capable of supporting 2400 bps with data compression, using the same network analog voice-grade channel.

　　Data Service Units (DSU)

　　DSUs are channel service units (CSI's) and data service units (DSUs) are required to connect digital customer premises equipment (CPE ) to carrier networks. A hardware device providing an interface between a digital line and a unit of data terminal equipment. DSUs provide transmit and receive control logic, synchronization and timing recovery across data circuits. DSUs may also convert ordinary binary signals generated by CPE to special bipolar signals. Bipolar signals are designed specifically to facilitate transmission at up to 1.544 Mbps rates over UTP cable, a media originally intended for 3 kHz, voice bandwidth signals. See Channel Service Units (CSU).

　　Data Terminal Equipment (DTE)

　　DTE is any device that can send data, receive data or perform both functions. (Note: sometimes DTE implies digital terminal equipment, a type of CPE used with digital Service——see CSU and DSU.)

　　DB Loss

　　Decibel (dB) is a unit of measure of signal strength, usually the relationship between a transmitted signal and a standard signal source. Loss is measured when the signal received across a communication circuit is less than what was transmitted by the signal generator.