Ericsson RBS 2106 Hardware Reference Manual page 341

7(10)
The equipment connected to the terminals should be insulated relay contacts.
A closed contact (logic zero) is required to be below 2 kΩ, and an open
contact (logic one) is required to be above 100 kΩ.
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 and sTRUs.
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.
External Sync. (Freq. Ref.)
This interface is used for connecting an external frequency reference. It uses a
generic synchronization port for the synchronization information.
Optional Output
This interface enables control of up to eight devices, which can be of various
types. These outputs are accessed through the upper backplane connector.
Optional Input
This interface enables connection of up to eight internal cabinet signals, such
as alarms. These inputs are accessed through the upper backplane
connector.
IOM Bus
2
This interface consists of three individual I C ports. It is used to communicate
with the CDU, CXU and cabinet ID.
EN/LZT 720 0244 R1A