Roy Smith wrote:

In article ,
While we're on the subject of 'juice' so to speak, in every power outage
up here in the north country [upstate NY] the phones are mercifully
still much welcomed operation but, here's the thing, while it's common
knowledge that the phone system wires carry their own juice, well, even
those wires have to have a source for their power generation! Where is
it and note that even in extensive power grid failures like the nation
just experienced, the phones came through! So where is their source?

All telco gear that I've ever heard of runs on 48V DC, supplied by huge
banks of lead-acid batteries. The batteries are constantly being
recharged from commercial power (what's known as "float service"). If
you lose commercial power, there's supposed to be enough battery power
to keep things going for 24 hours.

In addition, central offices and other switching facilities have
emergency backup generators. As soon as the commercial power goes down,
the generators are supposed to crank up and keep things going for as
long as the diesel fuel holds out.

Of course, it doesn't always work that way. I remember something like
10-15 years ago, a major long-distance switch in Manhattan went down. I
don't remember the details, but it was a combination of a generator
either failing or being taken out of service for testing and an alarm
being disconnected. Power was lost and the switch kept on chugging for
about a day on battery without anybody noticing. Eventually, the
batteries were drained, and the switch died (at which point somebody
finally noticed). Unbeliveable stupidity. I assume heads rolled over
that.


Thank you, Roy! I've often found that questions float around [this one
in fact came up during the recent outage] which folks, myself inclusive,
take for granted the known 'phones still work during power outages' BUT
when my wife asked me the 'why' of that, well, it was one of those
tongue-in-cheek but true nevertheless '...can't say I'm familiar with
that, honey...' [*translation: dunno!] chestnuts. ;-)

Doc Tony
;-)