Identifying DS-1-level circuit variables

The primary elements of hardware interacting at the DS-1 level that can negatively affect the entire DS-1 circuit are

• Your DS-1-level multiplexer.
• The echo cancellers within the circuit.
• The card that provides the DS-level multiplexing at your carrier.
• If you have individual local loops for each of your T-1 circuits, your local loops are possible culprits.

Just as you do when troubleshooting at the DS-3 level, you must consider both the equipment that receives the circuit within your phone system and your carrier's hardware as the most likely culprits causing both quality and continuity issues. The copper wire that makes up the local loop is also a possible source of DS-1-level problems. If someone cuts through the cable that provides juice to your DS-1 circuit, everything riding through it is down hard. At the DS-1 level of a circuit, you encounter your first increase in software interaction.

Remember If your local loop is a DS-3 circuit, or any circuit larger than the level of the issue you have identified, the source of the problem is most likely not the wiring or optical cable used to provide your local loop. If your DS-3 circuit has continuity, it is a safe bet that the DS-1s within your DS-3 are safely being received by your carrier and delivered to your phone system without incident. The local loop is essentially an empty pipe as far as your local loop provider is concerned; the local loop provider interacts only at the highest level of the circuit to maintain the clocking and keep the circuit stable. Your local loop provider ignores the T-1s or individual channels (DS-0s) within the local loop, except for the possible interaction of echo cancellers at the T-1 or individual DS-0 level if the circuit is an ISDN circuit.