电信专业英英词典D-6

　　Direct Inward Dialing (DID)

　　DID is PBX-to-central office trunks that allow incoming calls to a PBX to ring specific stations without attendant assistance. DID greatly reduces the number of required console attendants, compared with systems in which all calls must be extended by console attendants.

　　Direct Outward Dialing (DOD)

　　DOD is PBX-to-central office trunks that allow outgoing calls to be placed directly by PBX stations.

　　Dispersion

　　In dispersive¹ media, dispersion are complex signals are distorted because the various frequency components² which make up the signal have different propagation characteristics and paths. Due to the finite conductivity of copper³, wire or cable media for guided wave transmission is fundamentally dispersive. Dispersion limits the upper bit rate that a medium can support by distorting the signal waveforms to the extent that transitions from one information state to another cannot be reliably detected by receiving equipment, (e.g., logical l logical 0 value changes).

　　DLCI

　　data link connection identifier

　　DOD

　　direct outward dialing

　　DQDS

　　distributed queue dual⁴ bus

　　DS"N" Digital Signal Hierarchy⁵

　　A time division multiplexed hierarchy of standard digital signals used in telecommunications systems. DS1 level in the hierarchy corresponds to a 1.544 Mbps TDM signal which comprises 24 DS0 signals. DS0 refers to individual digital signals at channel rates of 64 kbps. Four DS1 signals digitally multiplexed produce a DS2 level signal, containing 96 DS0 channels, and requires a transmission medium that supports 6.312 Mbps. A DS3 level signal results from the digital multiplexing of 7 DS2 signals, supports 672 DS0 signals and requires a 44.736 Mbps transmission medium. Finally a DS4 level signal supports 6 DS3 level signals, 4032 DS0 signals and requires a 274.176 Mbps transmission medium. The DS hierarchy accounts for non synchronism in the multiplexing plan, hence the term "asynchronous digital hierarchy" and the use of overhead bits. Note that bit rates at higher levels are not integer multiples of 64 kbps.

　　DSP

　　digital signal processor

　　DSS/BLF

　　direct station selection/busy lamp field

　　DSS

　　digital subscriber service

1 Dispersive   

adj. 分散的

参考例句：

• In many atomic fluorescence applications a non-dispersive optical system may be used. 在许多原子荧光法的应用中，可以采用非分散的光学系统。
• The wave are of course dispersive. 当然这种波是弥散的。

2 components   

（机器、设备等的）构成要素，零件，成分； 成分( component的名词复数 )； [物理化学]组分； [数学]分量； （混合物的）组成部分

参考例句：

• the components of a machine 机器部件
• Our chemistry teacher often reduces a compound to its components in lab. 在实验室中化学老师常把化合物分解为各种成分。

3 copper   

n.铜；铜币；铜器；adj.铜(制)的；(紫)铜色的

参考例句：

• The students are asked to prove the purity of copper.要求学生们检验铜的纯度。
• Copper is a good medium for the conduction of heat and electricity.铜是热和电的良导体。

4 dual   

adj.双的；二重的，二元的

参考例句：

• The people's Republic of China does not recognize dual nationality for any Chinese national.中华人民共和国不承认中国公民具有双重国籍。
• He has dual role as composer and conductor.他兼作曲家及指挥的双重身分。

5 hierarchy   

n.等级制度；统治集团，领导层

参考例句：

• There is a rigid hierarchy of power in that country.那个国家有一套严密的权力等级制度。
• She's high up in the management hierarchy.她在管理阶层中地位很高。