HT9172 -- DTMF Receiver
The HT9172 is a Dual Tone Multi Frequency (DTMF) receiver device which includes an integrated digital decoder and band split filter functions as well as power-down and inhibit mode operations. The device uses digital counting techniques to detect and decode the full range of 16 DTMF tone pairs into a 4-bit code output. Highly accurate switched capacitor filters are utilised to divide the DTMF dual tone frequencies into low and high group signals. An integrated dial tone rejection circuit is provided to eliminate the need for pre-filtering.