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6-8 61200290L1-1G
Section 6, Loopbacks MX2800 M13 Multiplexer User Manual
Metallic Loopback
A Metallic Loopback test loops the entire DS3 back to the local loop side. The end effect of this test is a
loopback of all T1/E1s after being fully multiplexed and de-multiplexed to and from a DS3 and passed
through both directions of the DS3 LIU. During this test, the incoming DS3 is disconnected from the DS3
receiver and the outgoing DS3 signal is substituted in its place. See Figure 6-11 on page 6-8 for an illustra-
tion of this test.
NOTE
The DS3 Line Length should be set to Short before performing this
loopback.
Figure 6-11. Metallic Loopback Test
Remote Loopback
A Remote Loopback performs a loopback on the far-end M13 multiplexer. This loopback is available only
when the DS3 is configured for C-bit parity framing since it requires the availability of the FEAC channel.
See ANSI T1.107.
NOTE
Local timing must be selected before initiating this loopback. If
necessary, it may be returned after loopback has been cancelled.
Remote All T1/E1
A Remote All T1/E1 loopback performs a loopback of all T1/E1 channels on the far-end M13 multiplexer.
If an MX2800 is located at the far end, an Analog Loopback is executed on all active channels simulta-
neously. The form of this loopback code sent to the far-end will depend on the framing mode being used.
When in C-Bit parity mode, the MX2800 will send loopback commands over the FEAC channel. When
operating in M13 framing mode, the MX2800 will send C-Bit loopbacks at the DS2 level.
DSX-3
LIU
M23
MUX/DMUX
M12/G.747
MUX/DMUX
(1 of 7)
F
R
A
M
E
R
D
S
2
F
R
A
M
E
R
D
S
3
....
....
T1/E1 LIU
(1 of 28)
CODEC
(28 of 28)
CODEC
(1 of 28)
T1/E1 LIU
(28 of 28)
DSX-3
LIU
M23
MUX/DMUX
M12/G.747
MUX/DMUX
(1 of 7)
F
R
A
M
E
R
D
S
2
F
R
A
M
E
R
D
S
3
....
T1/E1 LIU
(1 of 28)
CODEC
(28 of 28)
CODEC
(1 of 28)
T1/E1 LIU
(28 of 28)