There are some formal rules for this that vary from country to country. In
Canada the rules are outlined in two Department of Communications documents
CS-01 and CS-02. The amount of power you can steal on hook is very small to
still stay legal, off hook is more or less 10 ma  at 6-7 volts. (Off hook
voltage is 5-7volts into a 600 ohm load) If you try to draw too much on hook
current the line will go off hook (the phone company thinks you want a line)
Stealing power is not as much of a problem with the carrier as impedance
mismatch. As a design consideration remember that you can also get line
voltage reversals

w..

michael brown wrote:

> DISCLAIMER:  I fully understand that the concepts that I am presenting
> are not well aligned with the "rules".  I only wish to do this as an
> experiment in the interest of learning a few things, not to try and mass
> produce an unsafe telco device.
>
> Art wrote:
> > I can't offer any additional comments regarding the actual quan of
> > elections you can capture:>:
> >
> > But, Maxim has a ready to go power supply that is designed
> > specifically for this purpose and there is lots of tech-talk in the
> > Ap Note regarding the phone lines.
>
> Thanks for the information, I will be looking into that.  I'm thoroughly
> convinced that my plan "can" work, now whether I can make it work, we'll
> have to see.  ;-)  When ringing, I'm sure that I can pick up some "free"
> power there and not upset the phone company too much.  I have a
> transparent phone that has a mechanical bell and a bunch of neon type
> bulbs that flash when it rings, IMO that's a bunch of power available
> that could be put to better use.
>
> I'm thinking that a slow drain (a few tens of uA's) from the line will
> give me enough power to have the pic sleeping and all other circuitry
> powered down while waiting for a ring.  With a dc blocked transformer
> over the line, I should be able to rectify and capture enough of the
> ringing signal to provide plenty of booster power to bring up the
> caller-id chip and an LCD display for at least a minute.
>
> michael (phreakin' ;-)
>
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