Revision 01
March 31, 1998
150-412-181-01
30
PairGain Engineering - Plant Series
HRU-412 List 8A
A Smart-Jack loopback causes the T1 interface chip to transmit the AIS
pattern to the NI and back to the HRU-412 List 8A T1 receiver circuit. The
T1 input to the HRU-412 List 8A at the XMT port is disconnected and
terminated in 100 ohms. The AIS pattern is examined by the HRU-412
List 8A for its overall integrity. The Smart-Jack loopback lasts about 100
milliseconds and terminates in one of the following conditions:
1
Pre-loop failed: if the transmit and receive patterns (all 1s) do not match,
there is a problem in the HRU-412 List 8A. The HLU declares an HRU
pre-loopback fail condition. This terminates the loopback test and returns
the HRU-412 List 8A to its unlooped normal state, indicating a defective
HRU-412 List 8A at the HLU.
2
Pre-loop passed: if the transmit and receive patterns do match, an HRU
pre-loopback pass condition is declared. All active circuits are working.
The metallic loopback relay remains closed and a logic loopback within
the HRU-412 List 8A is enabled.
Logic loopback is required in order to present the all 1s pattern to the CI and
at the same time to loop the signal received from the network back toward the
network. The HiGain system is in the AIS/ENA Smart-Jack loopback state. It
remains in this state until a loopdown command is detected or the default time
out period (if enabled at the HLU) expires.
When the HRU-412 List 8A is in the AIS/ENA Smart-Jack metallic loopback
state, the T1 input LOS, Code, and Frame monitoring circuits are connected
to the unframed AIS pattern, which is being looped back to these circuits
through the loopback relay. The CPE input signal is no longer monitored,
since the input circuit is open and terminates in 100 ohms. This forces the
FRM LED off and the LOC LOS LED off. The CODE LED indicates AMI if
the HLU CODE option is set to AUTO or AMI. It indicates B8ZS if the
CODE option is set to B8ZS. The AIS/ENA metallic loopback scenario tests
all of the HiGain system’s active circuits and fully conforms to
TR-TSY-000312.
When the HRU-412 List 8A is in an AIS/DIS Smart-Jack metallic loopback
state, the T1 input LOS, Code, and Frame monitoring circuits are connected
to the network signal, which is being looped back to these circuits through the
loopback relay. The CPE input signal is no longer being monitored, since the
input circuit was opened and terminated in 100 ohms. The FRM and LOC
LOS LEDs indicate the status of this signal from the network. The CODE
LED indicates the code (AMI or B8ZS) if the CODE option is set to AUTO.
It indicates AMI or B8ZS if the CODE option is set to AMI or B8ZS,
respectively.
Summary of Contents for 150-1103-81
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