You can connect the board in loopback mode to test the digital trunk application without connecting to the telephone network. The following illustration shows the loopback configuration that connects trunk 1 to trunk 2 using a crossover cable on a TX 5000E board:
The crossover cable connects the transmit signals from one trunk to the receive signals on another trunk by connecting the pins as shown.
If your board configuration uses two optional dual trunk adapters to access trunks 3 and 4, you can connect the adapter cables in loopback mode. Use the crossover cable to connect the transmit signals on one of the adapter cables to the receive signals on the second adapter cable as shown in the following illustration:
