[clug] linux Digest, Vol 92, Issue 62

Mike Carden mike.carden at gmail.com
Thu Sep 2 03:17:40 MDT 2010

I have been trying to resist putting my oar in this particular water,
but I have succumbed to temptation.

I'm a tad skeptical about 110VAC being present on a phone line for any
length of time. As Jason points out, ye olde Ring voltage was 90VAC
rms if I remember my years in the industry correctly. So, at least in
theory, 110VAC would mightily annoy you with constant ringing. Mind
you, more recent incarnations of telephone exchanges, remote
integrated multiplexers and voodoo phone equipment have probably
altered those specs somewhat.

And I'll sort of take issue with 9VDC. Again, Once Upon a Time, the
open circuit DC on a phone line was 48V (add up those huge 2V
lead-acid accumulators at the exchange) and the closed loop (off-hook)
voltage depended on the impedance (okay, resistance) of your Customer
Equipment (phone/fax/modem/etc). Most of the Panasonic gear I worked
with would sit at 12~15VDC when all's well.

I have been busy working on a domestic phone line when 90VAC of
incoming call decided to wake me up more than once. It's *very*
unpleasant, but not life-threatening. I reckon 110VAC via the
resistance of typical phone wiring would be similarly annoying but not

And I have no idea what any of this might have to do with Bob's radio
reception. I've been waiting for one of this list's radio amateurs to
chime in with advice for Bob.


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