| Glossary: D |
| DACS |
See Digital Access Cross-Connect System.
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| 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.
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| 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.
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| 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.
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| DATP table |
"The system configuration chart for the 3210 and 3216 Access Control Shelves in the MTAU |
| DATS |
Digital-Analog Test System
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| DATS maintenance |
"The process of setting up |
| DAU |
DSL Analyzer Unit
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| DBM |
Database Manager
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| dBm (decibels above one milliwatt) |
A logarithmic measure of the electrical power referred to one milliwatt.
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| dBm0 |
Decibel level relative to TLP
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| dBrn |
Decibels above reference noise
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| dBrn (decibels above reference noise) |
"The noise power relative to one picowatt |
| dBrnC |
"The power |
| DBS |
Database Screen Editor
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| DCD |
Data Carrier Detect
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| DCTE |
Data Circuit-Terminating Equipment
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| DCN |
Data Communications Network
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| DCP |
Detached Control Processor
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| DCS |
See Digital Cross-connect System.
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| 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
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| DDF |
Digital Distribution Frame
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| DDM |
Digital Data Multiplexer
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| DDS |
See Digital Data Service.
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| 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.
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| Decibel (dB) |
The unit for measuring the relative power of a sound or strength of an electrical signal on a logarithmic scale.
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| 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.
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| Demodulation |
The process of restoring a signal to its original form at the receiving end of a transmission system.
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| DHCP |
Dynamic Host Configuration Protocol
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| 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.
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| 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.
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| 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.
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| Digital Signal at Level 1 |
See DS1
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| Digital Signal at Level 3 |
See DS3
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| 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.
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| 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.
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| 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.
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| Digroup (digital group) |
A basic group of PCM channels assembled by time division multiplexing (TDM). Usually derived from 1.544-Mbps PCM-multiplex equipment.
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| Distributed Sniffer System (R) |
A network of analyzers remotely controlled from a number of hosts and/or workstations.
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| DLCI |
Data Link Connection Identifier
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| DMI |
Data Mode Idle
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| DMS |
Digital Multiplex System
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| DMT |
Discrete Multitone (modulation)
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| DN |
Directory Number or Distribution Network
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| DNS |
Domain Name System
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| 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.
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| DNT |
Do Not Test
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| DO |
Drop Out
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| DPMU |
Hekimian's 3249 Digital Performance Monitoring Unit
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| DPT |
Distributed Physical Test
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| DPU |
See DS1 Performance Unit.
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| DS0 |
Digital signal at the 0 level. A BPNRZ signal at the 64-kbps rate.
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| 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.
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| 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
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| 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.
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| 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.
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| 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.
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| 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.
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| 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.
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| DS3 Test Unit |
The Hekimian 6305 test set that provides complete monitoring and testing capabilities for in-service and out-of-service DS3 circuits.
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| DSE |
Data Switching Exchange
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| DSLAM |
Digital Subscriber Line Access Multiplexer
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| DSP |
Display System Protocol or Digital Signal Processor
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| DST |
Data Station Termination
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| DTCI |
Digital Trunk Carrier Interface
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| DTMF |
See Dual-tone Multifrequency.
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| DTR |
Data Terminal Ready
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| 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.
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| 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."
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| DX signaling |
"A long-range |
