ADTRAN MX2800 STS-1 - Analog Network; Figure 6-3. Tributary Loopback Test; Figure 6-4. Analog Network Loopback; Tributary

MX2800 STS-1 User Manual Loopbacks, Section 6
VT/Port Loopbacks
61204659L1-1A 6-3
Tributary
A Tributary loopback loops the selected VT/Port back to the network (STS-1). The T1/E1 is looped back
through the STS-1 mapper. During this loopback, the corresponding DSX-1/E1 input is overwritten by the
outgoing DSX-1/E1 signal. Figure 6-3 provides a diagram of this test.
Figure 6-3. Tributary Loopback Test
Analog Network
An Analog Network loopback test (Figure 6-4) loops the selected T1/E1 back to the network (STS-1). The
T1/E1 is completely de-multiplexed, looped back at the T1/E1 line interface unit (LIU) through the LIU
drivers and receivers, and multiplexed back onto the STS-1 network stream.
Figure 6-4. Analog Network Loopback
STS-1
MAPPER
T1/E1 LIU
(1 of 28)
T1/E1 LIU
(28 of 28)
STS-1
LIU
CODEC
(1 of 28)
CODEC
(28 of 28)
STS-1
MAPPER
T1/E1 LIU
(1 of 28)
T1/E1 LIU
(28 of 28)
STS-1
LIU
CODEC
(1 of 28)
CODEC
(28 of 28)