It's nice to know when it's actually a fellow dumbass and not a fucking clanker.

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.

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.