Eli5: how does a cord landline work when the power is out?


Like the phones that have a special plug and everything, the cord one still work when the electricity is out and they don’t seem to have batteries in there, so how and why do they still work

In: 142

The phone company generates power at their central office with which they supply their network.

The line supplies it’s own power, separate from the mains power. IIRC, [edit: incorrectly – see downthread] the line sits at 3v, goes up to 24v on ring, and 9v when off hook.

I used to take advantage of this and use my landline to power various small electronics that I wanted to stay on if the power went out.

On the power poles, the telephone line is in the thicker bundle lower down the pole, so it’s less likely to get damaged.

A subscriber loop in a “plain old telephone service” (POTS) system carries its own 48 volt DC power, supplied by a bank of batteries in the central office.

I worked for AT&T and can vouch that the Central Office has giant batteries that supply power (and usually a generator as well).

The batteries sit in giant barrels…they’re huge! I mostly did residential installs so didn’t get a chance to go into a CO often, but all the servers and battery vats and everything were very cool.

Good old days. Now almost all the pots lines have been removed in favor of digital, no internet, no power no phone, also “voip” doesn’t fall under the same protections as a landline so a court order is not need to pull records or even calls.