Identifying circuit variables in circuits that are DS-3 or larger

Your multiplexer (MUX), the carrier's multiplexer (at the level of your circuit - DS-3 MUX for a DS-3 circuit, OC-12 MUX for an OC-12 circuit, and so on), and the physical connection between the two pieces of hardware handled by the provider of your local loop interact at the DS-3 level and higher.

Remember If alarms ring on your DS-3 multiplexer, and the entire network span is down, a DS-1-level issue is not bringing down your circuit.

Similarly, if you have a problem with a T-1 circuit or on an individual channel on a single T-1, the problem can't be caused by the provider that supplies your local loop or with the DS-3 MUX. This is because DS-3 and DS-1 circuit problems don't interact at the individual DS-0 channel level. If your entire DS-3 has static on it, you must investigate the multiplexers on either end of your local loop. If you have a continuity issue and the span is down, the problem might lie with any of the cross-connects created by the local loop provider, or it could be a defect in the multiplexer at either end.