Testing in loopback mode

Use a loopback configuration for your TX 4000C board to test your digital trunk application without actually connecting to the telephone network.

Use a punchdown block with eight RJ-48C trunk connectors and a crossover cable to set up the loopback configuration. Connect the cable from the TX 4000C to the punchdown block and then to the loopback cable on the punchdown block.

The following illustration shows the TX 4000C loopback configuration with a punchdown block connecting trunks 7 and 8 using crossover cables:

 

The crossover cable connects the transmit signals from one trunk to the receive signals on another trunk as shown in the illustration.

Each of the RJ-48C trunk interfaces has the pinouts shown in the following illustration:

 

The following illustration shows how the connector is wired on a loopback cable: