Nortel Passport 4400, Using Manual, Page: 126 / 144

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206906-D Rev 00 4.2
virtual circuit between data networks. (Also known as Data Network
Address.)
DRAM
Dynamic Random Access Memory. Readable/writable volatile memory
device in which data must be periodically refreshed (electrically) to be
retained.
drop and insert
A process whereby DS0 channels received from one T1 or E1 interface are
dropped within the T1 or E1 voice module and replaced with new information
destined for the other T1 or E1 interface. Applies only to T1 or E1 voice
modules with dual T1 or E1 ports.
DS0
Digital Service, level 0. The 64-kbit/s international line standard format as
defined by the ITU-T, for digitizing one voice conversation.
DS-1
Digital Service, level 1. The 1.544-Mbit/s interface defined in ITU-T G.703.
Consists of a framed pattern of twenty-four 64-kbit/s timeslots, as specified in
ITU-T G.703. (Also known as DS1.)
As used with Passport 4400 voice service, refers to the network end of the T1
line interfacing with the T1 voice module. See also, DSX-1.
DSU
Data Service Unit. Data communications equipment that connects data
terminal equipment to a digital phone line. (Also known as Digital Service
Unit.)
DSX-1
Digital Signal Cross-connect frame. As used with Passport 4400 voice
service, the local end of the T1 line interfacing with the T1voice module. See
also, DS-1.
DTE
Data Terminal Equipment. In industry usage, the user equipment on a
subscriber link that is a source or destination of transmitted data. A DTE
device typically connects to a DCE device.