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Digital Interfaces
Issue 5 January 1998
8-5555-230-024
Digital Communications Protocol
Digital Communications Protocol (DCP), a forerunner of ISDN-Basic Rate Inter-
face, has been the architectural foundation for Lucent Technologies digital serv-
ers and switches. It provides advanced ISDN-like functions by integrating voice
and high-speed data. DCP continues to serve as a key digital interface for
DEFINITY ECS.
Like ISDN-Basic Rate Interface, DCP defines the communications interface
between a terminal and the switch. It consists of two 64-kbps information (or
bearer) channels and a separate 8-kbps channel for signalling and control infor-
mation (or data channel). Out-of-band signalling via the data channel allows the
information channels to be used for clear-channel transmission.
DCP’s framing structure allows voice, data, and signalling information to be trans-
mitted with low overhead and virtually free of errors. DCP transmits at a rate of
8,000 frames per second or 160 kbps. DCP allows data and digitized voice to be
multiplexed on one or two twisted pairs, terminating in a standard telephone jack.
Digital Multiplexed Interface
DEFINITY ECS supports high-speed, efficient data communications through
Lucent’s Digital Multiplexed Interface. Digital Multiplexed Interface allows com-
munications between a terminal and host computer, between a switch and host
computer, and between two host computers.
Digital Multiplexed Interface is consistent with ISDN-PRI. 24 64-kbps channels
(one of which is reserved for signalling information) transfer data between two
endpoints through the DEFINITY ECS. The multiplexed channels can be sent
over standard Digital Signal Level 1 facilities, allowing the host computer to be
located remotely.
Digital Multiplexed Interface offers two major advantages. It delivers a standard,
single-port interface for linking host computers internally and externally via T1
carrier. And, since it is compatible with ISDN standards and is licensed to numer-
ous equipment manufacturers, it promotes multi-vendor connectivity.
DEFINITY ECS supports two versions of Digital Multiplexed Interface, each differ-
ing in the way information is carried over the 24th channel:
■ Digital Multiplexed Interface-bit-oriented signalling carries framing and
alarm data and signalling information for connections to host computers
and other vendor equipment.
■ Digital Multiplexed Interface message-oriented signalling, fully compatible
with ISDN-PRI, uses the same message-oriented signalling format, Link
Access Procedure on the D-channel, as ISDN-PRI for control and
signalling. These signalling capabilities extend the advantages of Digital
Multiplexed Interface-Message Oriented Signalling multiplexed
communications to the public ISDN network.