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Posted: Tue Jun 21, 2011 4:14 am
How do i encode a digital signal into DTMF? i'm currently working on a dial alarm for a college project. i'm storing a phone number in a microcontroller (89c51 or a pic) and dialling that number. i currently have a CM8880 chip, but i don't know the circuit which encodes digital input into DTMF. could someone please help me out here? i have the data sheet but its not of too much use.
Posted: Tue Jun 21, 2011 7:30 pm
Posted: Wed Jun 22, 2011 6:35 pm
Posted: Thu Jun 30, 2011 12:55 pm
DTMF was never designed to modulate digital signals. It is actually the sum of two Analog tones used in the days before any digital equipment was around. The reciever listened to these analog audio tones and decoded them into one of 16 results.
That being known, it should be possible to encode 4 bits into 16 tones and demodulate that on the other side, thats apparently what the links describe.