User Manual

Demand Assignment
System Overview GSI 003
605-0000-450
Draft Issue 1.3dr Date 8/02/00
Page 5 of 8
9.3. CT Equipment Rack Shelves:
9.3.1. Modem Shelves
Each Modem Shelf terminates one RF Channel, supporting up to 15 radio links,
provides an E1 network interface with the Access Concentrator and a V.24 (RS232)
Network Management interface to the Sitespan. Redundant E1 links can also be
provided to maintain the backhaul link to the Access Concentrator if the main link fails.
Up to two Modem Shelves can be equipped within the DA Rack and a further two
Modem Shelves placed in an Expansion Rack to support a total of 60 radio links and
four network management interfaces. The number of traffic channels supported will
depend on the bit rates for each circuit.
Each Modem Shelf has:
• Power Supply Units (PSUs). Two PSUs are used to supply power to the modem
shelf. The DC load is shared between PSUs and in the event of the failure of a PSU
the other PSU maintains power to the shelf.
• Analogue Card (AU). The AU Card converts the coded signals from the Modem
Cards to a base band signal (for the RF Card in the RF Combiner Shelf) and supplies
the TU Card with the recovered 2MHz clock signal.
• Shelf Controller Card (SC). The SC Card provides the management interface
between the Sitespan and the Modem Shelf. It also holds the configuration details in
NVRAM.
• DA Tributary Unit (DTU). The DTU Card provides the interface between the
Access Concentrator equipment and AS4000 Radio System for traffic and signalling
information.
• Modem Cards Up to six Modem Cards provide the core SS-CDMA modem
functionality interfacing traffic channels between the TU Card and the Analogue
Card and management signals to the Shelf Controller Card.
• LED/Alarm Panel, The LED/Alarm panel provides LEDs that reflect the overall
status of the system and an key switch used to acknowledge that a fault condition is
receiving attention.