hi this is about detecting dtmf on MT 8870

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hi all,
       i read a post on this group...i want to detect caller id on my
telephone line and i thought that using the MT 8870 was a good idea so
i got hold of the circuit and the datasheet .but i was unable to
detect caller id on my telephone...i counld detect a single digit. can
anyone tell me if there are certain requirements for this ic to work?
(like the incoming signal should only be dtmf and not modulated or
something of the sort..) any help will be most welcome...Anand Dixit.
p.s. : are there any ic that detect FSK based caller id??? or convert
the FSK signal to some other data format???

Re: hi this is about detecting dtmf on MT 8870

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Caller ID in the US is 1200 baud Bell 202 tone modulation.  It is a 1200
baud modem signal but with no time to learn the protocol like regular
modems do.

If your not in the US you had better do a web search on "Caller ID" to
be sure if your country uses a different standard.

Your MT 8870 is DTMF which is how the touch tone numbers in the US are
sent.  So it would only be usefully in the US for monitoring the number
you call.


Gerald Bonnstetter    Bonnsoft

Re: hi this is about detecting dtmf on MT 8870
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The caller ID is hung on as either a leader or trailer tone (I
forget which) to the AC ring burst.  At least in the US and Canada.

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Re: hi this is about detecting dtmf on MT 8870

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Sent between the first and second ring -- in Canada, they
probably do it between the second and first ring ... ;-)   eh?

mikey



Re: hi this is about detecting dtmf on MT 8870
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  and with Bell Canada you got to subscribe for it,(not free)

Re: hi this is about detecting dtmf on MT 8870

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Well, true here in the US too -- the phone companies are great
for add on "services" ...

Phone service ...... $20
voice on the line ... $10
Caller id ............... $9
Anon Call Block ... $0.35
various other things $10
total package ........."Priceless" ...



Re: hi this is about detecting dtmf on MT 8870
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They learned that trick from the US.  You realize that it costs
them more to suppress the signal than to let it through?  Until it
was legislated away, US telcos charged a premium for touchtone
service also.

--
Some useful references about C:
  <http://www.ungerhu.com/jxh/clc.welcome.txt
We've slightly trimmed the long signature. Click to see the full one.

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