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Glossary

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Term Main definition
D-channel
Delta channel. On ISDN networks, the channel that carries control and signaling information at 16Kbps for BRI ISDN services or 64Kbps for PRI ISDN services.
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D-ring
An item of hardware, usually a metal ring shaped like the letter D. It may be used at the end of a leather or fabric strap, or may be secured to a surface with a metal or fabric strap.
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D-type connector
A type of connector that connects computer peripherals. It contains rows of pins or sockets shaped like a sideways D. Common connectors are the DB-9 and DB-25.
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Daisy chain
In telecommunications, a wiring method where each telephone jack in a building is wired in series from the previous jack. Daisy chaining is not the preferred wiring method, since a break in the wiring would disable all jacks
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Dark current
The external current that, under specified biasing conditions, flows in a photo detector when there is no incident radiation.
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Dark fiber
An unused fiber; a fiber carrying no light. Common when extra fiber capacity is installed.
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DAS

Distributed Antenna System

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Data communication equipment (DCE)
With respect to data transmission, the interface that is used by a modem to communicate with a computer.
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Data packet
The smallest unit of data sent over a network. A packet includes a header with addressing information, and the data itself.
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Data rate
The maximum rate (in bits per second or some multiple thereof) at which data is transmitted in a data transmission link. The data rate may or may not be equal to the baud rate.
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Data-grade
A term used for twisted-pair cable that is used in networks to carry data signals. Data-grade media has a higher frequency rating than voice-grade media used in telephone wiring does. Data-grade cable is considered Category 3 or higher cable.
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Data-terminal equipment (DTE)
(1) The interface that electronic equipment uses to communicate with a modem or other serial device. This port is often called the computer
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Datagram
A unit of data larger than or equal to a packet. Generally it is self-contained and its delivery is not guaranteed.
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DB

Also known as D type/ D Sub/ D type Sub miniature
D type connectors are used as serial port connectors.

The D refers to the shape of the connector. A D9W connector for instance as you can see below means it is a 9 pin connection interface.

This connector also commonly comes as a 15 way or 25 way although can go up to a 72 way.

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DB-15
Standard 15-pin connector used with Ethernet transceiver cables.
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