Re: Why -48V for telephone lines, and not positive?

From: ILYA (ilya_sa_at_comtv.ru)
Date: 12/13/04 

Date: Mon, 13 Dec 2004 10:36:05 +0000 (UTC)

>>At least in Europe, most telephone exchanges use a negative voltage
>>referenced to good old mother Earth.
>>Why negative? Is it some 'cathodic protection' in case a pinhole leak
>>occurred?
>
> For > 99.9% of the time, my phone is on-hook, so one of the wires is
> at -48V (actually it's about -52V) and the other is within 1V of
> earth.

Some lands use another voltage levels...
For analogous local telephone network in my city:
  not hold 60V
  hold 6..15V
  ring ... up to 200V! (be careful!)
pair cable.