IMC Networks iMcV-DS3/E3/STS Operation Manual page 11

Loopback testing is useful for troubleshooting problems with network connections
should they occur. Looping received data back onto the transmit path helps
determine whether a connection is still valid. Remote loopback tests isolate problems
on the coax run between an iMcV-DS3/E3/STS module and the connected device,
while local loopback tests can isolate problems on the fiber connected to the module.
The following illustrations show a typical progression of loopback tests (i.e. starting by
checking the coax segment at the local side, then the coax segment at the remote
side, etc).
Pseudorandom Bit Sequence (PRBS) Testing
To test using Pseudorandom Bit Sequence, configure the iMcV-DS3/E3/STS modules
for No Loopback, then configure the Transmit Data Source to "Transmit
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