User Manual

Demand Assignment
System Overview GSI 002
605-0000-450
Draft Issue 1.3dr Date 8/02/00
Page 8 of 16
The Central Terminal consists of the following components:
2.1. The Antenna and Feeder sub-system
The antenna and feeder sub-system consists of either a two stacked dipole -high gain
omni-directional antenna, a 65° directional antenna or a 180°directional antenna
assembly mounted on a pole or mast and low-loss coaxial feeder cables which connect
the antennas to the CT equipment rack.
2.2. Central Terminal DA Rack
The Central Terminal DA Rack contains:
2.2.1. The RF Combiner Shelf
The RF Combiner Shelf forms the interface between the Antenna/Feeder sub-system
and individual Modem Shelves. The RF Combiner Shelf performs the functions
necessary to connect up to four RF signals to the Antenna/Feeder sub-system.
The RF Combiner Shelf supports up to 4 modem shelves two of those modem shelves
are contained in the CT Rack the other two modem shelves are contained in the
Expansion Rack.
2.2.2. Modem Shelves
The CT Rack accommodates up to two DA modem shelves. Each Modem Shelf
terminates one RF Channel, supporting up to 15 radio links, provides an E1 interface to
the Access Concentrator. The Access Concentrator provides CAS, V5.1 or V5.2
network interfaces with the Local Exchange. Each Modem Shelf also connects via a
V.24 (RS232) Network Management interface to the Sitespan network management
system. Fixed assigned modem shelves can be deployed into a demand assignment rack,
in this mode of working the rack can accommodate one DA modem shelf and up to
two FA modem shelves.