Let's see if we can shed some light on this subject, please.
I understand that CID (Caller ID) and EMWIN both use
a Bell 202 protocol. Could a Caller ID unit be used as an
EMWIN demodulator? Does anyone have suggestions for how
it would need to be modified? I presume the output from the
CID demodulating chip is TTL and would require a TTL to RS-232
level converter like the MAX232 or similar chip. Could anyone
some suggestions on how to interface the audio input? For example
would you need an isolation transformer or would a simple coupling
capacitor be sufficient? Where (which pin #) would I tap for the raw
data output from the demodulator chip? Would the TTL output need
to be inverted before converting to RS-232 serial output?
Does anyone have familiarity with any Caller ID units or the chips
used for Caller ID demodulating?
If you are not familiar with the EMWIN broadcasts by NOAA run a
search for "EMWIN" on YAHOO or any other search engine. You can
follow the links and learn everything you may want to know about the
system. By the way, old Bell 202 phone modems make excellent
If you can contribute to this discussion, please send me a response.