The line sits at -48V DC from CO battery strings, and when it rings you’ll see roughly 90 VAC at 20 Hz on a meter. That’s why during a 3 a.m. outage, there’s still dial tone — keeping connectivity for 911 and support comes first.
Saw ‘90 VAC at 20 Hz’ on my Fluke during a late-night ticket once and got a little zap before I switched the butt-set to monitor — use a high-impedance meter and keep fingers off the copper. Caveat: PBXs/ring generators can throw about 70–105 VAC at 20–25 Hz and long loops can skew things, so don’t treat the numbers as absolute. It’s the only time a phone line tries to high-five you.
During a 3 a.m. cut, ring hit 105 VAC — watch REN on old bells; RTs can brown out before CO, @pcarter51.
On those 3 a.m. outages, I pop the NID protector and meter at the test jack first; a leaky gas tube or an alarm seize can load the ring and make the plant look worse than it’s. Also watch for answer-supervision polarity flips on older remotes — your butt set will thunk and the readings jump if you’re not expecting it, @pcarter51.
I keep a neon ‘night-light’ across tip/ring at the NID — quick way to confirm cadence and catch a premature ‘ring trip’ from a wet splice or a security panel seize, @pcarter51. One caveat: some remote SLICs on skinny battery strings will drop dial tone long before the CO, so don’t assume every outage leaves POTS alive.
If you’re seeing 60–70 on ring and chasing ghosts, it’s often the meter — use a true‑RMS that specs ‘down to 20 Hz’ or a Simpson 260 and you’ll get an honest read; some remotes do run a bit lower, but rule out the tool first, @cwatson91.