Describing The Common Equipment - Comdial DSU II System Manual

IMI66–132
1.5

Describing The Common Equipment

The common equipment base unit for the DSU II digital telephone system is a fully electronic
device. It is essentially a special purpose computer system acting as a communications controller
between central office (CO), private branch exchange (PBX), or CENTREX supplied lines and
the proprietary digital telephone stations. The software design of the common equipment
provides complete system support and great flexibility of operation.
All DSU II systems have analog, loop-start line interfaces to the public switched network.
Special intergrated circuits (COder/DECoder or CODEC chips) in the line circuits translate
analog voice information to and from the digital domain. Internally, the system is fully digital
and has Pulse Code Modulation (PCM) highways that are time-division multiplexed into PCM
channels. Each digital station has two B-channels available for voice and/or data and one
D-channel available for telephone control. This arrangement is known as 2B+D. The system
maintains communication with the stations with digital loop transceiver circuits that are under
system software control. A time switch intergrated circuit, also under system software control,
routes calls, creates conferences, and set padding levels as required.
The common equipment consists of a base unit, which provides complete feature support, and
optional expansion modules for additional lines and stations. It is contained in a contemporary
metal housing designed to be inconspicuous in a modern office environment. It is engineered to
be wall or rack mounted.
1–8 Introducing The DSU II Digital Telephone System
DSU II Digital Telephone System