Uncle Monster wrote:

Correction, the main backup at phone company central offices
is banks of batteries. There are generators but the battery
banks can keep the phone service up for days. If anyone wants
to know about storage batteries, the phone companies have a
great deal of knowledge and experience. The battery rooms at
at phone company central offices would astound you.

Update! The large Central Office battery rooms are shrinking
fast:
Solid state equipment is more power efficient.
CO's are now unmanned.
CO only has 12-24 hr battery.
CO has no generator.
Lead and sulfuric acid are banned or hazmat.

It's much more cost effective to pull up a portable 50KW
Onan at the CO building and "plug" into the charger buss.
One portable can easily support a dozen COs during long,
wide area power outages and "parked" where needed.

The cell sites work the same way.

The phone companies are quietly doing away with the massive
lead liability they had. Find a piece of lead jacketed phone
cable these days, and figure the tons of lead leached from
aerial cable.

Your copper phone line is now powered from a local
neighborhood fiber fed "hut" or RemoteTerminal and a few
automotive sized batteries. It's not a big city thing
either, rural Adams County Pa now has many more RTs than COs!

All this new fiber stuff is moving the RT and terrabits to
your back door ;-)

-larry / dallas