Hi Daniel....and thanks for your reply.

The problem is happening to everyone (all phones, all lines, sporadic times)....however the common issue seems to be "hearing" the person you're speaking to (the person your speaking with continues to hear us).

I've not replaced the phone wiring (yet) as it was happening on all handsets (even mine when I was speaking with Spectrum). That is a good suggestion....I'll change that out on a couple of extensions to see if that resolves the problem for them.

I have several handsets (Comdial Impact) too....and will change out them with the same stations for the wiring. I'll just change a couple to see if the problem improves or stays the same.

Our entire phone system is on a battery backup (APC SmartUPS 1500 with a fresh APC OEM battery).....and the Spectrum equipment is on a battery backup they provided (small Tripp-Lite device).

Yes (power supply / low signal)....however, after speaking with them again today, they say the signal is good. They also changed out SOME of the cabling (and a cable distribution block)....but nothing "upstream" from our suite.

Thanks again for your assistance....I'll switch out a couple of the handsets, cords and stations per your recommendation.