Chris, the TCM1520A uses the ring cycles to charge a cap for the internal 5V
regulator so you don't need to (you can't) count cycles. By it's nature, it
ignores the first ring while charging, then switches the output level after the
ring burst.

   - Tom

At 11:09 PM 12/21/97 -0500, you wrote:
>To mask off the ring, you could count off a few of the cycles, figure at 20 Hz
>(sometimes 30), there are 40 (60) cycles in that first ring.  Count off five to
>make sure that the period is right and it ain't noise, and you could be in.  A
>crafty individual would then regenerate the ring back out and tack on the lost
>five cycles.  You could then look at the hook status and kill the added ringing
>cycles if the phone is answered.
>
>Chris
>Pioneer Microsystems, Inc.
>
>Tom Handley wrote:
>
>>   <snip>
>
>>    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.
>> >
>
>