To test the digital trunk application without connecting to the telephone network, connect the CG 6060 board in loopback mode. The following illustration shows the loopback configuration using a crossover cable to connect trunk 0 and trunk 1 on a four-trunk CG 6060 board:
The cross-over cable connects the transmit signals from one trunk to the receive signals on another trunk as shown.
If your board configuration uses two optional splitter cables to use trunks 2 and 3, you can connect the splitter cables in loopback mode. Use the cross-over cable to connect the transmit signals on one of the splitter cables to receive signals on the second splitter cable.