On 10 May 2003 at 9:07, Dave VanHorn wrote:

> At 09:57 AM 5/10/2003 +0300, Peter L. Peres wrote:
> >Use a JFET constant current generator set at 1mA instead of the resistor
> >imho.
>
> You can't draw that much at the on-hook condition, and pass part 68.
> 10 meg is what it takes.
>

        You can just load the line for say 1mS and measure the current to
know if the 48V is present. Did this with two optocouplers and a zener.

        Mark

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