DTMF-based Project

Thread Starter


Joined Apr 15, 2013
Hi guys
why protection circuit is needed in DTMF circuit when we use it with mobile phone ( zener diodes , capacitors , resistors )?

and how the filter section in the MT8870 decoder work ?

thanks in advance


Joined Dec 29, 2010
What kind of protection circuits are you talking about? DTMF signalling is very old and is mainly used in PSTN telephone signalling. AFAIK mobile phones dont use DTMF signalling anymore.

You can make use of MT8870 in your hobby projects by sending the tones via audio riding on RF frequency (eg FM transmitters) and be decoded by the receiving side to get back the original messages (numbers sent).

For the wiring you can refer to the datasheets of MT8870 and google for the schematics.