----- Original Message -----
From: Dan Michaels <oricom@LYNX.SNI.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Monday, August 21, 2000 3:14 PM
Subject: Re: [PIC]: Modulated pulses


> Dave VanHorn wrote:
> >>
> >> >D.C. Line Voltage (Talk Battery) - 48v with receiver on-hook, red wire
> >> >(ring) negative, 5v for off-hook (with 50-1000 ohm d.c. load on line).
> >
> >That off-hook number is pure imagination. You can get anything from
> >near-zero to ???
> >I've seen 6V to 18V across off-hook equipment. Mostly, it depends on the
DC
> >resistance of the telco line (an unknowable for you) and the instrument
> >(another unknowable, unless it's your design)
> >
> >--
>
> These should probably all be checked, if James is gonna cast them
> on techref, but I seem to recall 48v was supposed to be the nominal
> voltage applied at the telco end - miles of wire away.

Yep, and given that the DC resistance of an on-hook phone is nearly infinite
(relative to the wire to the TELCO) you'll see the 48v nominal across the
set.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

>
> - danM
>
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