Chris, I loss track of the originator of the topic but I've used the TI
ring detector (TCM1520A) and a PIC16C84 to monitor rings to a BBS for a local
Amiga user group. Basically, if I did'nt receive an `OK' signal from the Amiga
within a certain time, it would reset the BBS. There was a lot more to it but
the TCM1520A simplified the hardware while being fairly `bullet proof'...

   The nice thing about the TCM1520A is that it connects directly to the phone
line, has built-in suppression (1.5KV/200us), low ringer equivalence (< 1),
built-in 5V regulator suitable for logic or optoisolator applications, and the
diode bridge handles ring signals to 150V. In a typical application, you add
two capacitors and one resistor (two if you use an optoisolator).

   Back to the original question, you could use one edge of the ring detector
output to ignore the first ring.

   - Tom

At 02:02 PM 12/19/97 -0500, you wrote:
>Do I sense defeat?  Tisk tisk.  Why can't you use that TI ring detect chip (I
>forget the number, links a piezo to the phone line).  Then use a PIC (thus
I did
>not specify OT in the subject line) to detect the pulses, and based upon a
> switch
>on a pin that indicates ring/ don't ring, re-generate a piezo ring.  Then
rig it
>into your phones.  Ring signal is 2 seconds on, 4 seconds off.
>
>Chris Eddy
>Pioneer Microsystems, Inc.
>
>Wynn Rostek wrote:
>
>> At 03:47 PM 12/18/97 EST5EDT, you wrote:
>> >>         One should be careful about the type of load presented to a
>> >> telephone line pair.  The equipment at the switch to which your phone is
>> >> connected may range in complexity from rotary steppers and mechanical
> relays
>> >
>> >So basically, your saying that there is no practical, recommended way
>> >to cut off ringing from one extension on the inside wiring?  I
>> >thought this might be the case, and I would have to set up the ring
>> >blocker on the enterence point to the house.  Any other suggestions?
>> >
>> >
>>
>> Nah, even in the bad old days when Ma Bell made a marine drill sargent like
>> like a cub scout den mother, we used to disable a ringer by taking the case
>> off the phone, loosening the terminals and pulling a ringer wire off.  The
>> phone then "disappeared" from the scans. ;-)
>>
>> Wynn
>
>