Wow, thanks for all of the input! I have tried several things as a result:
1. One reply said that the tip side of my Verizon line is supposed to be at ground, but it isn't. So I tried jumping it directly to ground. This killed the hum and related problems when using line one of my two-line phone, but it also rendered the Verizon line unusable.
1a. There's a wire coming out of my NID with a bear end that is just hanging in mid-air. Is this supposed to be a ground wire???
2. I put ground lifters on my computer and all the devices connected to it. This only worsened the hum problem. It did lead me to find a loose ground in my breaker panel, though. My outlet grounds were reading 8 ohms to earth (water pipe). I fixed that, but it didn't reduce the hum.
3. The hum does not change when the wall transformer is disconnected (it powers the speakerphone, clock, and backlight).
4. I tried reversing polarity on each line, with no effect.
I agree that trying another phone or hooking this phone to two other lines would be the next logical step in troubleshooting the problem. I guess I am just cheap.
I thought there might be something I could connect to the lines to filter the hum or correct the imbalance.
The SNC engineers have assured me their Super SNIX device will do the trick, but it is almost $300. "Cheap" and $300 don't mix.
I find it curious that no one has mentioned a filter on the line. Is anyone out there familiar with the SNIX? It contains a common-mode choke and a harmonic drainage reactor. I can wind a choke if someone could recommend some specs. But I have no idea what a harmonic drainage reactor is. I am sure I could make one if I did. Any ideas?
Thanks again, all!
