Re: Telephone in use indicator Help


"steve" <stevesemple@xxxxxxxxx> wrote in message
news:1146931878.232250.162630@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Thanks for your comments.

I tested the voltage On Hook its 51 VDC. Off Hook its 51 VCD.

Same voltage both ways? No...

I have tested the four Diodes they seem to be ok. Closed one way .5 to
.6 Ohms the other way. If I understand it right.

Open one way, 0.6 volt (the diode test range on your meter reads in volts,
not ohms), is correct.

I have gone over the circuit one more time looking for human error.
Cant seem to see anything wrong.

The one thing I did not mention was that I am using the 2n4401 instead
of the MPSA-18, as the schematic suggests I can do.

2N4401 is reliable and should work.

I must say when I tested the resisters they do vary a lot when your at
the 22M size. My little digital meter reads them anywhere from about 21
to about 25. My meter has a 20M scale and then a 200. So I have to set
it on the 200M scale to test 22M. I figure its doing pretty good to get
in anywhere near 22M.

It's the meter's problem, not the resistors... It's hard to measure
resistances that high. I doubt there is anything wrong with the resistors.

Short of any other answers I could test the Transistors. But IM not
always sure I know what to look for or how acurate it is on my little
Digital MM. (which is all I have being a Novice.)

Does it have an hFE (transistor gain) measurement? If so, try that.

The reason I chose this circuit I suppose is because it looked
relatively simple and used an external power source which should last
for some time. Im always wary of all the warnings about causing
problems with stealing power from the poor phone company. And possible
other issues that can come up.

Any thoughts?

It looks like a reliable design, although a bit on the complicated side.

Please check over and over again for wiring errors. Even the best of us
make plenty of them.


.

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