The DTMF (dual-tone multi-frequency) decoder is plugged into the sockets for lC2 and lC3 on the 80C32 extension board. The ICs originally fitted at these positions are moved to the DTMF decoder board.

In the decoder designed for the DTMF Link project a Holtek HT9170B does the main job. The natural counterpart of the HT9200B used in the associated encoder (described elsewhere in this publication), ...

The objective of the project is to decode dual tone codes into digits which are later interpreted by microcontroller. This device is very useful for decoding Dual Tone Multi Frequency (DTMF) generated ...