hi this is about detecting dtmf on MT 8870

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???

Reply to
anand dixit
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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

Reply to
Gerald Bonnstetter

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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Reply to
CBFalconer

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

mikey

Reply to
Mike Fields

and with Bell Canada you got to subscribe for it,(not free)

Reply to
ryan wiehle

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" ...

Reply to
Mike Fields

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.

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CBFalconer

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