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GLOSSARY GL-11
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direct outward dialing
(DOD)
A feature that enables a communications-system telephone user to gain
access to the public network without the assistance of an attendant by
dialing an access code and receiving a second dial tone. The user can then
dial the desired public-network number.
distributed
communications system
(DCS)
An ETN and/or M/ST network linked in such a way that selected features
appear to operate as if the network were one system.
DMI-BOS See digital multiplexed interface with bit-oriented signaling.
DMI-MOS See digital multiplexed interface with message-oriented signaling.
DMI with message-
oriented signaling
(DMI/MOS)
Digital-multiplexed-interface (DMI) signaling in which the signaling in
the 24th channel is based on the definitions of strings of bits that form
messages. DMI/MOS is similar to the Integrated Services Digital
Network primary rate interface (ISDN-PRI). Also called message-
oriented signaling.
DS1 See digital signal level 1.
DS1 robbed-bit signaling See robbed-bit signaling.
duplex data link Electronic equipment that permits automatic transmission of digital
information between two points, in both directions simultaneously. See
also simplex data link.
EIA interface A standardized set of signal characteristics (time, duration, etc.) specified
by the EIA. Normally means a RS-232C interface.
EIA port A communications systems port circuit with a built-in data module which,
when used a Z3A ADU at the data terminal equipment (DTE) end of the
connection, extends the RS-232C serial interface to asynchronous DTE
over two pairs of standard voice grade wire without need for an
intervening modem or data module. Also referred to as a Data Line
Circuit.
electronic tandem
network (ETN)
A private network that consists of private and public trunking and
switching resources. ETNs often span geographic areas and consist of
private or leased transmission facilities that interconnect the customer’s
communications systems. An ETN uses Automatic Alternate Routing
(AAR) with a uniform numbering plan to address the various
communications systems and telephones in the ETN.
emulation A technique using software programming that allows one computer or
digital device to behave like another device.