[null and void]

Rings were caused by 40 volts DC flowing down that circuit. That voltage could knock you on your butt.

100V DC pulsed at 20 Hz.

Plenty enough to get your full undivided attention...

[Jamestown1630]

Is this why people were wary of being on the phone during thunderstorms?

[old-ager]

> 20 Hz

With, what, 400 Hz on top of that? That’s what created the ring sound heard by the caller. When I first heard the sound when farting around on an incoming line, I realized that the audio was connected to the caller while ringing and you could send audio back without picking up the line.

[Blueflag]

OK, ~64- 100+ volts depending on switch manufacturer and set up. Also DC experienced V drop over distance, splices, etc

IIRC, 40 volts was the minimum. IIRC. That was a while ago. RBOC career slot. Southern Bell.

Two 48V in series, tip and ring. Again IIRC.

Thanks for the clarity.