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              Outbreak Magazine Issue #10 - Article 10 of 18
           '~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~'

Specialized Common Carrier Service (SCCS)
contibuted by Adeamis

The DMS-250 Specialized Common Carrier Service (SCCS) provides the capability
of Analog to Digital (A/D) and Digital to Analog (D/A) conversions which are
necessary with analog circuits.  The DMS-250 can also switch voice and data
circuits.

The DMS-250 takes either analog or digitally encoded info and by using time
slot interchange, switches it from any input port to a temporary addressed and
connected exit port.  The info may or may not be converted back to analog.

Cellular Mobile Radio Service

A cellular system consists of two main parts:  a cellular switch and cell site
equipment.


Cellular Switching Systems

A cellular switch performs three main functions:  audio switching, cell site
control, and system administration.

The DMS switches provide three basic implementations for cellular switching:
Stand-alone, Combined, and Remote.

Stand-alone switching is done by a Mobile Telephone Exchange (MTX) which is
interfaced with one or more class 5 end offices.  The connection is made by
DID/DOD trunks.  Depending on the needs of the area, the MTX can be divided as
follows:  MTX which serves urban areas, MTXC which handles suburban areas, and
MTXM which is used for rural areas.

Combined switching is incorporated into a DMS-100 by some hardware additions
and cellular software.  Combined switching is designed to give an easy,
cost-effective way to install cellular services to an existing host.

Remote Switching is done by combining Remote Switching Center (RSC) with a
Cell Site Controller (CSC).  This combination is hosted by either a
stand-alone or a combined switch.  Remote Switching is designed for serving
suburban centers, remote areas, or a small community and it gives extra
flexibility for a growing system.

All of these cellular switches have the ability to balance the workload among
various cell sites.  For example, if one site's workload reaches the
programmable level of congestion, calls would be routed to nearby sites that
can handle the extra calls.


Cell Site Equipment

Cell site equipment consists of a CSC and radio equipment.  The CSC is
controlled by the cellular switch and it controls radio equipment and
maintenance tasks.  The CSC will work on any MTX cellular switch because of
the Remote Cluster Controller (RCC).

The radio equipment consists of self-contained Radio Channel Units (RCU),
antennas, transmitter multi-couplers, and receiver combiners.

By different program software, an RCU can perform voice, control locating, and
test functions.  The self contained nature allows the RCU be remotely located
to the CSC.  A RCU has built-in circuitry for extended testing of the radio
part of the system.



Cellular switching i didnt write it