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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Canada here: we moved last year and experienced exactly this when a strong storm knocked out power for half the day yesterday. Our landline runs through our ISP’s modem, and we had no signal. The mobile networks were spotty at best; calls were choppy, texts barely went though, and data was non-existent unless you sent a km or two away
The old telephone system had batteries that sent power over the phone line. If the power went out, the phone would have power unless the phone line was cut. How long they lasted depended on how many lines there were connected to it, how old the battery was, and how many calls were made. They could last a few hours to several days.
Many now have landlines through cable service. They have battery back ups too, either in a box on a pole or along the street, or in a box inside the house. They typically provide power for up to a day or so, if the battery is new, but there are several added connection between the house and the telephone system, and if any of those has lost power with failed backup power you still won’t get a connection.
Plain old telephone services (POTS, for real) phones don’t require any power unless they’re ringing or somebody’s talking.
When you would receive a call, there’s literally a switch that closes a circuit, and from the telephone central office (CO, the closest facility serving your area) that circuit sends 105V to the phone, triggering the clapper to rattle back and forth against the bells, making it ring.
When you took the phone off the cradle, a different switch was triggered to start the lower voltage powering the ear and mouth (E&M) circuit.
Back at the CO, these switches were in two-post racks, and there were rows of batteries much like car batteries that provided the power. There was a regular power line to the CO, charging the batteries, but of course in a power outage, the batteries would keep working for some time.
If you want to keep going, https://en.m.wikipedia.org/wiki/Telephone_exchange
They don’t take much power to run. The lines that run to the phone to connect them to the phone company also have a power wire that runs into them. The power is supplied by the phone company who have back up power in the event of an outage.
Rather than being powered by the electricity in your home, power is provided to the phone network at the exchange end of things.
So instead of plugging your phone into a plug in your home, you are plugging it into the end of an extension lead that reaches all the way back to the phone company.
What this means is that if you have a localised power cut, it may not affect the location of the exchange providing per through your phone line, so your phone will still continue working as normal.
And for the times where a pretty cut does affect the exchange, they have backup systems in place to keep the phone network powered – using batteries or generators for example – so that it can still be used and provide a method of contact in emergencies (assuming of course the end user isn’t using personal devices that are reliant on local power).
Batteries is the answer, i did a tour of am exchange about 20 years ago and they still used open wet cell batteries.
Lead acid chemistry batteries have a voltage of ~2V, car batteries have 6 of these in serial. Capacity comes from the lead plate service area so they are big round drums.
In the exchange 24 were lined up in series to provide 48V and multiple strings to provide. This filled an entire room and due to the nature of them they generate hydrogen which leads to a very flamable enviroment that needs to be well ventillated else they go boom. These days sealed cells are used in 4x12v battery strings.
The reason for the big strings is to provide the amperage, which while its low per line, its a lot of phone lines per exchange. The big amperage led to busbars that if you drop a spanner/screendriver on will flash vaporise/melt/arc. While ive not seen this i have had stories from guys that worked in exchanges in south africa that had a little less regulation than Australia.
48V is still used quite heavily in telecommunications big core router/switches as AC powersupplies dont go big enough
I’d love to see the submarine cable landing stations that provide several thousand volts to the submarine cables.
(I work in telecommunications)
In fiber to the home scenarios, the battery is in the demarcation box. In a fiber to the neighbourhood scenario, the batteries will be in a service box on the street. Otherwise, the batteries will be in the Central Office.
Secondary question: Could you steal power from landlines?
I have not seen a POTS line in probably 20 years. Do they still install them? I guess they exist some places. I can only imagine the tel cos have about -100% interest in keeping this around.
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.
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