There will be a big battery bank in each telephone exchange that supplies power until the generators start up. I always hated the battery room, it smelled and there was always the danger of hydrogen buildup. The telephone exchange can keep running on generators until mains power comes back on, or the fuel runs out. (The longest outage I’ve experienced personally on generators was 3 days). The expectation is always that mains power will be restored “soon”.
Because the phone company (miles away from you and your local power outage) still has power, or has battery backups and automatic generators. The phone runs off of 48v that is sent directly via the phone line. That’s why you don’t need to plug your landline into a power outlet. It was also historically a fairly important safety feature, as people tend to need emergency services after their power goes out. For instance, maybe a bad storm blew through.
This actually turned out to be a problem when telecoms started transitioning towards digital phone lines. These days, they usually send everything via coax or fiber. Then a modem will take that incoming line and decode it into phone, internet, and TV signals. The modem also provides that 48v power on the phone lines. But that presents an issue, where a power outage will kill the customer’s modem, and therefore kill the customer’s landline phones. And we’ve already established that landline phones are an important safety fallback during emergencies. So now, you can actually get battery backups directly from the telecom, to be able to keep your modem powered (and thus use your landline phones) even during power outages.
My house has a landline phone connected to the internet modem via a VoIP box. My entire house has battery backup so the modem, router, and phones stay on during a blackout, but the equipment my modem talks to (I’m assuming somewhere on the street) does not have a battery backup, so the phones are still useless in a blackout.
Battery backups and diesel generators at the interchange, both of which are only temporary. Batteries need to be charged and diesel needs to be pumped, and while you can (and most infrastructure resiliency relies on it) operate these systems on manual power, the stability of large infrastructure systems becomes quite vulnerable once it’s necessary to run a diesel generator to pump diesel for your other diesel generators.
~~Old school landline phones work without power. Not saying they’re using them, just a fun fact. ~~
Edit: see below. I have no idea what in talking about.
They absolutely do not. They just don’t require power locally, but there’s 48v on the line that needs to be generated somewhere.
There will be a big battery bank in each telephone exchange that supplies power until the generators start up. I always hated the battery room, it smelled and there was always the danger of hydrogen buildup. The telephone exchange can keep running on generators until mains power comes back on, or the fuel runs out. (The longest outage I’ve experienced personally on generators was 3 days). The expectation is always that mains power will be restored “soon”.
Then why would our landline work when the power was out?
Because the phone company (miles away from you and your local power outage) still has power, or has battery backups and automatic generators. The phone runs off of 48v that is sent directly via the phone line. That’s why you don’t need to plug your landline into a power outlet. It was also historically a fairly important safety feature, as people tend to need emergency services after their power goes out. For instance, maybe a bad storm blew through.
This actually turned out to be a problem when telecoms started transitioning towards digital phone lines. These days, they usually send everything via coax or fiber. Then a modem will take that incoming line and decode it into phone, internet, and TV signals. The modem also provides that 48v power on the phone lines. But that presents an issue, where a power outage will kill the customer’s modem, and therefore kill the customer’s landline phones. And we’ve already established that landline phones are an important safety fallback during emergencies. So now, you can actually get battery backups directly from the telecom, to be able to keep your modem powered (and thus use your landline phones) even during power outages.
My house has a landline phone connected to the internet modem via a VoIP box. My entire house has battery backup so the modem, router, and phones stay on during a blackout, but the equipment my modem talks to (I’m assuming somewhere on the street) does not have a battery backup, so the phones are still useless in a blackout.
Battery backups and diesel generators at the interchange, both of which are only temporary. Batteries need to be charged and diesel needs to be pumped, and while you can (and most infrastructure resiliency relies on it) operate these systems on manual power, the stability of large infrastructure systems becomes quite vulnerable once it’s necessary to run a diesel generator to pump diesel for your other diesel generators.
Oh… I had no idea… But it makes sense! Thanks for the info, friend 😃