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Tests
Channel Local Loop
Channel Local Loop commands the DSU to loop data back to the DTE at the channel interface.
Local Loopback checks everything up to the channel interface. During this test the DSU clamps the
channel data it transmits to the T1 link to marks.
Local Loop can be commanded by means of the terminal interface, by SNMP control, by means of
front panel switches, or by the LL lead (Pin 18) of the DTE interface.
Note
Tests cannot be performed by means of front panel switches when the front panel has been inhibited by
an SNMP controller or by the terminal interface. Front panel enabled is the default condition.
The DTE interface LL lead can only command Local Loop if Channel EIA Test Leads has been enabled
by an SNMP controller or by the terminal interface. The default condition is disabled.
INS
L
I
N
E
SD
BPV AIS
OOF NS
TM
T1
CH
RL
M
O
N
553
Figure 4-20
4-18
2. TM indicator On while Local Loop is active.
ON
1. To start test from front panel, press CH momentary
action switch.
I
N
CH indicator is lit during the test.
O
Press switch again to end the test.
U
T
RSP
RD
3. Enter test data at the DTE. Compare data entered at
the DTE with data looped back and displayed by the
EQ
DTE. (Test equipment can be connected in place of
the DTE.
ALM
DTE
or
Test
TX
Device
RX
Channel Local Loop
SpectraComm 553 Fractional T1 DSU
Installation and Operation Manual
SC 553 DSU
TX
Driver
DTE
Inter-
Framer
face
Analog
Receiver
Channel Tests
076R155-000
Issue 7
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