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
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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.
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.
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.
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.
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