Say what?
Methinks that something got lost in the translation.
That part's true. POTS uses +24VDC TIP and -24VDC Ring.
48 VDC on the line but 96 PDC ring voltage. I'm not certain how it is done now but they used to use a ring generator to put out the 96 PDC. PDC meaning pulsating DC current which would allow the old style Bell phones with bell ring and a capacitor across the bell it to ring.
There were several good reasons for DC on phone lines. First is noise. DC doesn't produce A/C hum. Second is the older switching systems were mechanical relays. Big huge bays of them. To avoid their lines from picking up A/C hum the wires both in the cable on the pole and even the phone wires in the home are actually twisted across each other. That is why you should use phone station wire and not thermostat wire too hook up a phone jack.
I was not questioning that, rather I was questioning the assertion that the "inherent stability" of DC power as opposed to AC power was "part of the reason that landline phones often survive storms better than the electric grid"...
Negatory. Telco runs on hook at -48VDC on ring nominally but upwards of -52VDC is allowable due to voltaic loss across distance. You see the real reason for DC in phone systems is because the nature of analog communications works better with DC than AC. When you go off hook a switch detects the short from the phone completing the circuit and the voltage drops to about -9 to -15VDC off hook.
The ohms resistance across the loop has to be within certain thresholds for the switch to detect the short. I can’t recall the specs on a modern 5ESS switch but that’s why the further out you go the lower the gauge. So if you’re 15 miles from the main office you can expect 19ga copper.
The twisting on the pair is to reduce Induction between the pairs and AC systems. If you run voltage over a copper wire it’ll induce across any line running parallel.
Also with DC telecom you need to balance the pair and have the same capacitive length on each side to reduce noise.
Telephone work is easy though. But doing it well is the hard part.