Transmission Interface Handling DS1 1544 kbit/s
Sending the loopback deactivation codes above minimizes the risk
for faulty loops to be left in the network (in the RBS neighbour
nodes) as result of loop activation codes sent when the Multidrop
Bypass function is enabled.
• The LLB and PLB may co-exist in the RBS, but the LLB will be
used. The PLB will be in use after release of the LLB. A PLB
can be set as a “background” loop to an LLB. The universal
loopback deactivate code releases both loops. A received AIS
releases also both loops.
Line Loop Back (LLB)
The Line Loop Back is a loopback in which the signal returned towards
the source of the loopback command consists of the full 1.544 Mbit/s
signal. The loop includes no jitter attenuation. The bit sequence
integrity will be maintained for the signal and no change in the framing,
and no removal of bipolar violations.
The LLB is supported by two specific commands:
1. The command “Line Loopback Activate” sets the line loop.
The code word “00001110 11111111” received five times in a
sequence will make an action to connect a line loopback. The
rightmost bit is received first.
2. The command “Line Loopback Deactivate” releases the line loop.
The code word “00111000 11111111” received four times in a
sequence will make an action to disconnect a line loopback.
Payload Loop Back (PLB)
The Payload Loop Back is a loopback in which the signal returned
towards the source of the loopback command consists of the payload of
the received signal. The signal has the bit sequence integrity retained
and newly generated ESF framing, but not necessarily maintaining the
integrity of the channel time-slots of the received signal.
The PLB is supported by two specific commands:
1. The command “Payload Loopback Activate” sets the payload loop.
The code word “00010100 11111111” received five times in a
sequence will make an action to connect a payload loopback.
2. The command “Payload Loopback Deactivate” releases the
payload loop.
The code word “00110010 11111111” received four times in a
sequence will make an action to disconnect a payload loopback.
Universal Loopback Deactivation Signals
1. The command “Universal Loopback Deactivate” releases all loops
whether they are of type LLB or PLB (or both).
212 (306)
EN/LZT 123 2697 R5A
1998-08-13
© Ericsson Radio Systems AB
— All Rights Reserved —
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