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Triple DS3/STS-1 I/O Front Module
Plexus 9000 Planning and Engineering Guide
Issue 2, March 26, 2004
Section 130-120-500
5-140
Telica,
Inc.
The rear DS-3/STS-1 modules contain relays that pass the DS-3/STS-1s
either to the front module or to the protection bus. The rear protection
module obtains the DS-3/STS-1 from the protection bus and passes it to
the front protection module.
5.11.3.10
DS-3 and STS-1 Loopbacks
DS-3 or STS-1 loopbacks can be used as diagnostics to test line integrity.
Loopbacks are always line loopbacks that loop the entire DS-3
(44.736 Mb/s) or STS-1 (51.84 Mb/s)
signal. Loopbacks can occur at the
near or far end facility. The Plexus 9000 can respond to as well as initiate
loopbacks. The Plexus 9000 only responds to remote loopback requests
when operating in C-Bit mode. Likewise, FEND loopbacks on a DS3 port
can only be issued when operating in DS-3 C-Bit mode. See
loopbacks of the near-end. Loopbacks are initiated or cleared using TL1
commands.
DS3
Receive
DS3
Transmit
DS3 LOOPBACK
SUPER
MAPPER
LIU
To/From
TSU/FSU
P249-AA
03-06-01
Figure 5.11-3. DS-3 Near-end Loopback
STS-1
Receive
STS-1
Transmit
STS-1 LOOPBACK
SUPER
MAPPER
LIU
To/From
TSU/FSU
P474-AA
05-10-01
Figure 5.11-4. STS-1 Near-end Loopback