At 08:15 AM 12/18/97 -0500, you wrote:
>Hi all.
>
>So from what I see, this circuit SHOULD keep the line seized forever.  Don't
>you want to stay above the 48 volt battery voltage the fone company
supplies???
>
>
>Regards,
>Jack Warren
>

<snip>

>> ----------/\/\/\------------|--------
>>                            ___
>>                             ^
>>                             |
>>                             V
>>                            ---
>>                             |
>>                             |
>> ---------/\/\/\----------------------
>>

Jack,

This circuit will never allow the phone line on right end of the diagram to
jump above Vznr+.6 in either polarity, where Vznr is the zener voltage of
the diodes. If you use zeners with Vznr of say 55 V, then this circuit
should allow normal phone operation but should clamp rings.
Now, this circuit will affect the line on the left side of the diagram,
too, however its effect will be reduced slightly due to the resistors, but
if the resistors are low enough,( I guess around 50 to 100 ohms), then this
circuit might be able to stop all ringing in the house. The best value of
the resistors depends on the way the house is wired. Probably trial and
error would be the best way to find out the values.

I do have one question for all the phone gurus out there, though: How long
does it take, from the time that the handset on a phone is picked up, 'til
the phone company considers that the call has been answered. In other
words, is there a slight chance that this clamping circuit might actually
answer the call in some systems? I doubt it myself, but I think some more
opinions are needed.

Sean


+--------------------------------+
| Sean Breheny                   |
| Amateur Radio Callsign: KA3YXM |
| Electrical Engineering Student |
+--------------------------------+
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