The HM 9270C/D is a complete DTMF receiver integrating both the bandsplit filter and digital decoder functions. The filter section uses switched capacitor techniques for high- and low-group filters and dial-tone rejection. Digital counting techniques are employed in the decoder to detect and decode all 16 DTMF tonepairs into a 4-bit code. External component count is minimized by on-chip provision of a differential input amplifier, clock-oscillator and latched 3-state bus interface.