General DataComm SpectraComm 553 Installation & Operation Manua page 33

Operation
T1 (T1 Local Test) - Momentary switch. When
pressed, places the DSU in a T1 Local Test that
loops back channel data at a T1 interface. The
loopback occurs at whichever T1 interface,
network or cascade, the channel data is
directed to by the unit's configuration. LED is
lit while this test is in progress.
When pressed and held for 2 seconds,
activates QRS self test signal for the loopback.
LED blinks while this test is in progress.
Press switch a second time to end a test.
TM indicator blinks for QRS errors during
self test.
RL (Remote Digital Loop) - Momentary switch. When
pressed, causes the DSU to send a PN127
loopback command to the remote unit. LED is lit while
this test is in progress.
The DSU can perform a remote digital loopback test
with any compatible device that recognizes the
command.
When pressed and held for 2 seconds, activates QRS
self test signal for the loopback. LED blinks while this
test is in progress.
Press switch a second time to end a test.
TM indicator blinks for QRS errors during self test.
Figure 3-2
076R155-000
Issue 7
Front Panel Controls
SpectraComm 553 Fractional T1 DSU
Installation and Operation Manual
Controls and Indicators
ON
INS
I
L
N
I
N
O
E U
T
RSP
SD
RD
EQ
BPV AIS
OOF NS
TM ALM
T1
CH (Channel Test) - Momentary switch.
CH
When pressed, places the DSU in a Local
Loop (transmit data looped to receive data
RL
at the DTE interface). LED is lit while the
test is in progress. Press switch a second
time to end test.
TX
M
O
RX
N
The test signal to be directed through
this loopback must be provided externally.
553
3-3