Manual Part 6

DXU-21
5 Interfaces
This section describes the signal and power interfaces, and the operator
interface, of the DXU.
5.1 Signal and Power Interfaces
Transmission Interface
The four transmission interfaces are connected to the BSC (Protocol GSM-Abis)
or to cascaded base stations. In cascade mode, this interface can control
an external bypass relay. Unused time slots can be through-connected to a
successive base station. The communication speed in E1 interfaces is 2 Mbit/s
and in T1, 1.5 Mbit/s.
External Alarm Inputs
Through this interface it is possible to connect up to 15 binary alarms (16
including one dedicated alarm). This interface is found on the upper backplane
connector.
The equipment connected to the terminals should be insulated relay contacts.
A closed contact (logic zero) is required to be below 2 k
, and an open contact
(logic one) is required to be above 100 k
.
The current through a closed 0 contact is 1.2 mA.
The alarm contacts connected to the external alarm inputs should be insulated
and have a current range above 1.2 mA. The voltage between terminals with
an open contact is +24 V DC.
Local Bus
The local bus is a time slot and multidrop bus, where the DXU-21 is the master
of the bus. Two identical local buses are implemented, with common frame
synchronization and clock signals. The interface is accessed through the lower
backplane connector. The local bus is used for TRUs.
Timing Bus
This interface is used for distribution of timing information to the TRUs through
the backplane. The interface is accessed through the lower backplane
connector. The timing bus is only used for TRUs.
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EN/LZT 720 0244 Uen R3A