cgordon@vpnet.chi.il.us (Crash Gordon) (11/24/90)
I need to access a computerized switching system (yes, I'm authorized!) via
a modem for testing purposes. The system is intended for use by people, not
computers. To gain access, you must dial an access code _after_ the first
ring, but _before_ the second ring. This is a pretty narrow window to hit
accurately.
I have a modem made by Practical Peripherals which uses a set of three chips
made by Rockwell. The IC numbers are: R5311-29, R5310-38, and 10464-16.
I'm assuming this is the much-touted "Rockwell Chipset" I've read about in
modem ads and reviews...
The modem has a command ("AT@") which waits for a ring followed by 5 seconds
of silence. This is almost what I want, except that I can't wait 5 seconds.
(There would be another ring, and I'll have missed that window.) I've tried
peeking at the 8051 code which drives the modem, but it's a big haystack and
a small needle to try and change that 5-second delay.
My best hope at this point is that the modem chipset will output a logic
level when some supervisory tone is detected on the line. (Similar to the
function of the Teltone M980 IC.) If I can find this pin, I can route it
out the RS232 port and detect the ring signals in the host software. Which
pin would carry the signal I'm after?
Please note that I need to know when the _distant_ phone is ringing.
Detecting an inbound ring is pretty simple.
Any help appreciated!
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Gordon S. Hlavenka cgordon@vpnet.chi.il.us
Crash Electronics, Inc. (708) 963-8088
140 S. Lincoln "A Westmont Tradition
Westmont, IL 60559 for Over a Quarter!"