- on Miscellaneous Electronics
- Published in issue 7/2010 on page 26
8-channel DTMF Link: Decoder
(Summer Circuits 2010 article)
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 HT9170B is a Dual Tone Multi Frequency (DTMF) receiver with an integrated digital decoder and bandsplit filter functions. Then IC uses digital counting techniques by means of a 3.58 MHz crystal to detect and decode all the 16 DTMF tone pairs into 4-bit words.