TeleCom Glossary

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Glossary: D
DACS See Digital Access Cross-Connect System.
Data communications equipment (DCE) The interfacing equipment sometimes required to couple the data terminal equipment (DTE) into a transmission circuit or channel. Also couples a transmission circuit or channel to the DTE. Also known as Data Circuit-Terminating Equipment.
Data Exchange Interface (DXI and DXI/SNI) "(DXI) An SMDS interface between the customer and the network used at low speeds
Data port The point of access to a computer that uses trunks or lines for sending or receiving data.
Data service unit (DSU) "A device that transmits digital data on transmission facilities. Typically
Data terminal equipment (DTE) Equipment consisting of digital end instruments. Converts user information into data signals for transmission. Also reconverts received data signals into user information.
DATP table "The system configuration chart for the 3210 and 3216 Access Control Shelves in the MTAU
DATS Digital-Analog Test System
DATS maintenance "The process of setting up
DAU DSL Analyzer Unit
DBM Database Manager
dBm (decibels above one milliwatt) A logarithmic measure of the electrical power referred to one milliwatt.
dBm0 Decibel level relative to TLP
dBrn Decibels above reference noise
dBrn (decibels above reference noise) "The noise power relative to one picowatt
dBrnC "The power
DBS Database Screen Editor
DCD Data Carrier Detect
DCTE Data Circuit-Terminating Equipment
DCN Data Communications Network
DCP Detached Control Processor
DCS See Digital Cross-connect System.
DCS Concentrator "A device used to collect the test access digroups (TADs) of many digital cross-connect systems (DCSs). Once the TADs have been collected in one location
DDD Direct Distance Dialing
DDF Digital Distribution Frame
DDM Digital Data Multiplexer
DDS See Digital Data Service.
DDS Test Unit (DTU) The Hekimian 6302 test set that provides bidirectional DS1 and DS0A/DS0B interfaces. T1 and subrate access and testing require these interfaces.
Decibel (dB) The unit for measuring the relative power of a sound or strength of an electrical signal on a logarithmic scale.
Degraded minute A minute is considered degraded if it has all SES removed and has more than 93 CRC-6 violations or 93 frame bit errors.
Demodulation The process of restoring a signal to its original form at the receiving end of a transmission system.
DHCP Dynamic Host Configuration Protocol
Dialback number "The phone number associated with the automatic error reporting function of a DTAU
Dialog "An operational routine that uses commands to automate system functions; for example
Digital channel A transmission channel that carries signals in digital form.
Digital cross-connect system (DCS) "A sophisticated digital switch. It can switch an entire T1 line
Digital Data Services (DDS) "A 56- or 64-kbps digital channel that provides private line
Digital loop carrier (DLC) A digital transmission system designed for subscriber loop plant. Multiplexes a plurality of circuits onto very few wires or onto a single fiber pair.
Digital Remote Test Unit (DRTU) "The Hekimian 6700 test system that provides complete monitoring and testing capabilities for digital circuits (DDS
Digital serving area (DSA) "The combined geographical serving areas of a set of DDS serving offices. The appropriate tariff(s) specifies this area. The DDS office serving areas that make up a DSA are not necessarily continuous. Also
Digital signal A signal that has a limited number of discrete states before transmission.
Digital Signal at Level 1 See DS1
Digital Signal at Level 3 See DS3
Digital system cross-connect (DSX) "An internal interface that acts as a central point for cross-connecting
Digital Test Access System (DTAS) Hekimian's family of digital access and test equipment.
Digital Test Access Unit (DTAU) A subset of digital access and test equipment included in Hekimian's DTAS product line. This equipment provides split and hitless monitor access to T1 lines for maintenance and testing.
Digital Test Access Unit Plus (DTAU+) A subset of digital access and test equipment included in Hekimian's DTAS product line. This equipment provides hitless access to T1 lines in both the monitor and split modes.
Digroup (digital group) A basic group of PCM channels assembled by time division multiplexing (TDM). Usually derived from 1.544-Mbps PCM-multiplex equipment.
Distributed Sniffer System (R) A network of analyzers remotely controlled from a number of hosts and/or workstations.
DLCI Data Link Connection Identifier
DMI Data Mode Idle
DMS Digital Multiplex System
DMT Discrete Multitone (modulation)
DN Directory Number or Distribution Network
DNS Domain Name System
DNS Server A computer that translates a host into a network address so the table of names and addresses does not have be stored in each host.
DNT Do Not Test
DO Drop Out
DPMU Hekimian's 3249 Digital Performance Monitoring Unit
DPT Distributed Physical Test
DPU See DS1 Performance Unit.
DS0 Digital signal at the 0 level. A BPNRZ signal at the 64-kbps rate.
DS0-DP Digital Signal at 0-level Data Port channel unit. A plug-in circuit pack that recovers a DS0 signal for further connections. Its input and output signals are at 64 kbps.
DS0A "A DS0 signal that carries data for only one customer. For subrates
DS0B "A DS0 signal that is the same as a DS0A signal when carrying 56-kbps customer data. However
DS1 Digital Signal at Level 1
DS1 (Digital Signal at Level 1) "A digital transmission format in which 24 voice channels are multiplexed into one 1.544 Mbps (USA) T1 digital channel or
DS1 framing errors Frame synchronization bit errors detected by the Model 6302 DTU in either terminal framing (Ft) or signaling framing (Fs) bits.
DS1 Performance Unit (DPU) The Hekimian 6301 test set that provides complete in-service monitoring. This test set also provides out-of-service testing of DS1 signals.
DS1 Signal Access Unit (DSAU) "A plug-in circuit pack used in DDS hub offices. This unit provides full duplex access to a DS1 signal
DS3 (Digital Signal at Level 3) A digital transmission format in which 28 DS1 signals are carried on a T3 facility at a rate of 44.736 Mbps or on an E3 (CEPT) facility at a rate of 34.368 Mbps.
DS3 Frame A group of bits sent serially over a communications channel (or facility). A DS3 frame consists of 56 blocks of data; each block contains 84 bits of information prefixed by one overhead (framing) bit. The overhead bit has a variety of uses.
DS3 Idle Signal A framed signal with a …1100…payload pattern transmitted when the terminal (or network element) equipment is inactive. Frequently used as the DS3 keep-alive signal for network test resources.
DS3 Test Unit The Hekimian 6305 test set that provides complete monitoring and testing capabilities for in-service and out-of-service DS3 circuits.
DSE Data Switching Exchange
DSLAM Digital Subscriber Line Access Multiplexer
DSP Display System Protocol or Digital Signal Processor
DST Data Station Termination
DTCI Digital Trunk Carrier Interface
DTMF See Dual-tone Multifrequency.
DTR Data Terminal Ready
Dual-tone multifrequency (DTMF) "Signaling that uses a simultaneous combination of a lower and higher group of frequencies to represent each digit or character. The lower tones are 697
Duplex A facility which permits transmission in both directions simultaneously. Also called full-duplex.
Duty cycle "The percent of a single pulse period (for a ""1"") during which the voltage is nonzero. The ratio between actual pulse width and the total available time slot."
DX signaling "A long-range
 

 

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