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 T echnologies digital serv-
ers and switches. It provides advanced ISDN-like functions by integrat ing 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 inte rface
between a terminal and the switch. It consists of two 64-kbps informatio n (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 tran smission.
DCP’s framing structure allows voice, data, and signalling informati on 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 Interfa ce
DEFINITY ECS supports high-speed, efficient data communications through
Lucent’s Digital Multiplexed Interface. Digital Multiplexed In terface 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 channe ls
(one of which is reserved for signalling information) transfer data betwe en two
endpoints through the DEFINITY ECS. The multiplexed channels can be sent
over standard Digital Signal Level 1 facilities, allowing the host com puter to be
located remotely.
Digital Multiplexed Interface offers two major advantages. It delivers a sta ndard,
single-port interface for linking host computers internally and externally vi a T1
carrier. And, since it is compatible with ISDN standards and is li censed to numer-
ous equipment manufacturers, it promotes multi-vendor conne ctivity.
DEFINITY ECS supports two versions of Digital Multiplexed Interface, each differ-
ing in the way information is carried over the 24th chan nel:
■Digital Multiplexed Interface-bit-oriented signalling carries framing a nd
alarm data and signalling information for connections to ho st 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 adva ntages of Digital
Multiplexed Interface-Message Oriented Signalling multiplexe d
communications to the public ISDN network.