The S5T3170 is a complete Dual Tone Multiple Frequency (DTMF) receiver that is fabricated by low power CMOS and the SwitchedCapacitor Filter technology. This LSI consists of band split filters, which separates counting section which verifies the frequency and duration of the received tones before passing the corresponding code to the output bus. It decodes all 16 DTMF tone pairs into a 4bits digital code. The externally required components are minimized by on chip provision of a differential input AMP, clock oscillator and latched three state interface. The on chip clock generator requires only a low cost TV crystal as an external component.