Multiple-tone detector with CCD filters

Describes an IC multiple tone detector which is made of three transversal CCD filters with nonoverlapping bandpass characteristics for tone separation and each filter has an internally matched threshold level for reproducible tone detection. The chip was fabricated in the BMOS double layer polysilicon technology, operates on three power supplies and a master clock, measures 85/spl times/283 mils and dissipates only 100 mW of power.