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

396 views

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

24 Answers

Anonymous 0 Comments

UPS – uninterrupted power supply (powerful back up batteries). Used to work at banks and all of them have it to run the switches and servers.

Anonymous 0 Comments

The phones in your house worked off of power supplied on the phone lines. 48V DC on hook and then uses 90VAC at 20hz to make the phone ring.

With digital phone service through a cable company, a device called an eMTA, embedded multimedia terminal adapter, that has a modem and analog converters to provide that voltage to you phones.

Fiber ONT solutions would use an ATA, analog terminal adapter, to do the same thing.

Anonymous 0 Comments

For the basic phone systems over a copper pair, there is a generator back at the office where the dial tone is also generated. With a derived voice system (phone via data) installers will put UPS (back up battery) at the residence.

Anonymous 0 Comments

First, **the corded phones are simple machines, powered by the signal in the phone line itself.** The phone system is basically a second set of power lines with a dedicated purpose. The sound is sent as vibrating electrical signal like a speaker or headphone cable. Other signals, like punching a number, is just a specific sound, that devices are tuned to respond to.

**As long as the phone company keeps their lines up and powered, it will keep operating**, entirely independent of the electric grid. The phone company often runs it’s own generation, since they require a fairly consistent supply and are already centralized so it’s much cheaper.

**If the power grid goes down due to supply/demand issues** (e.g. hot summer day overloaded by ACs, power plant failure, …), **the phone grid is liable to stay up** as it’s not as susceptible to this failure. If a tree falls on your neighborhood lines, however, it’ll take everything out together and you’ll be completely disconnected.

Anonymous 0 Comments

the telephone line itself supplies power. spikes and drops in voltage on the line determines if it’s busy calling or free.

Anonymous 0 Comments

# Because it was powered by the Telco, not your house. Unless the telco lost power, it still had it.

Anonymous 0 Comments

*IF* your landline service is from the telephone company and they are still wired for POTS (literally “Plain Old Telephone Service”), their system has its own voltage over the wires, independent of the electric utility.

Increasingly, even so-called “landlines” are VOIP (“Voice Over Internet Protocol”) which runs via your internet router. so if your phone service is from a company like Comcast, or in some areas also AT&T, if the power goes out your router goes out, so your so-called “landline” is also dead.

Anonymous 0 Comments

The telephone cable supplies a very small minimal amount of energy required by the landline to work. This is arranged by the telephone provider.

In a similar spirit we also have Power over Ethernet PoE. Which allows power to be transmitted over ethernet wires. So even when the lights go out, your internet access doesn’t.

Anonymous 0 Comments

Those old phone lines carry (a little bit of) power, enough for the phone.
When you have a power outage you lose the power supplied by high voltage lines to your home, but that’s completely separate from the phone lines.

Anonymous 0 Comments

The simplest answer that is true is that the electricity is provided through the phone line. Phones did not need to be plugged into a power outlet until answering machines (voicemail for the ignorant) got built into the landline phones.