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.
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.