atcomsystems.ca/forum Forums TDM Business Telephone Systems Avaya - Lucent Telephones & Systems Troubleshooting old Partner ACS...will this work?

Are these POTS lines? Trouble on all lines? I would start at the NID during their off hours and make 20-30 test calls on each line.
Even if it's intermittent you have a good chance of finding the trouble with a bunch of test calls.
IME, if the trouble is on all the lines it's usually the system.