Use Caller ID as an EMWIN demodulator?

Use Caller ID as an EMWIN demodulator?

Post by rbw » Fri, 13 Nov 1998 04:00:00

Here's an interesting idea to kick around in the newsgroups.
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
EMWIN demodulators.

If you can contribute to this discussion, please send me a response.
Thanks.
--Bob

 
 
 

Use Caller ID as an EMWIN demodulator?

Post by Paul Gro » Sat, 14 Nov 1998 04:00:00


On Thu, 12 Nov 1998 15:37:29 -0600,
in the newsgroup rec.radio.scanner,

from  thoughtfully posted:

Quote:> Here's an interesting idea to kick around in the newsgroups.
> 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?

Most Caller ID chips contain all the modem "stuff" in one chip.
The raw "serial" outputs are not available. The outputs of these
chips are usually "microwire" or IIC outputs - not RS-232 type
"serial".

If the "stuff" coming in does not follow the Caller ID protocols
- the chip is probably going to ignore it.

Quote:> Does anyone have familiarity with any Caller ID units or the chips
> used for Caller ID demodulating?

See this page:

 http://www.hut.fi/Misc/Electronics/telephone.html#signaling

Check Motorola, Mitel and M/X-Com. MX-Com makes many modem chips.

Quote:> 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
> EMWIN demodulators.

The chips used for amateur "Packet Radio" will work - such as
TI's TCM3105 - a favorite of packeteers.

A simple solution is to use a "Baycomm" type packet modem - such
as the Ramsy kit - but you will need to re-wire the serial
connector or make an adapter.

Cheers,
Paul Grohe

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 Paul Grohe                     National Semiconductor Corp.
 Assoc. Analog Apps Engineer    2900 Semiconductor Drive
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