Identifying DS-0 or individual channel issues

Individual channel issues generally indicate a problem with either your multiplexing hardware or the cards your carrier uses in its switch to perform the multiplexing. You can identify a DS-0 issue pretty easily. If your DS-1 is working fine and many channels on the DS-1 can send and receive calls without any problem, there are really only two main variables and one minor variable to evaluate in determining the source of the problem.

The main variables at the DS-0 level are the multiplexers on either side of the circuit that break down the T-1 into individual channels. If your third DS-0 on your T-1 has static, is unavailable, or if you can't seize a dial tone on it, either your hardware or your carrier's hardware is failing for that channel. If you can isolate both pieces of hardware and the problem doesn't clear up, the only other likely candidate is possibly an echo canceller somewhere in your circuit that is malfunctioning or dying a slow death. The purpose of an echo canceller (also referred to as an echo can) is to eliminate the echo heard on a call. If the device is failing or was provisioned incorrectly, it can prevent your call from completing with good quality, or at all.

You can also encounter problems at the individual call level caused by software compatibility in the outpulse signaling and start. If your system is configured for loopstart and your carrier is set for E&M Immediate, you will have problems making calls. This type of configuration issue causes calls to suddenly disconnect, fail to connect at all, and otherwise fouls things up. Configuration issues at the individual call level can also cause frame slip errors and errors that can take down your entire circuit.