4 ms·
Such as land line phones which still have power even in a blackout it's separate from power lines. The phone line power must be AC I can't see such long runs b
by dghughes 12y ago
Such as land line phones which still have power even in a blackout it's separate from power lines.
The phone line power must be AC I can't see such long runs being DC.
- YupItsAUsername 12y agoActually, it's 48 volts DC (http://en.wikibooks.org/wiki/Communication_Systems/Telephone_System#Line_Cards http://en.wikibooks.org/wiki/Communication_Systems/Telephone...). A few years ago I got to tour a central office for a small telephone/cable company in a suburb of Houston and the phone lines were actually powered directly by massive banks of lead-acid batteries which were then constantly kept floating by the mains supply.