The MT8870D/MT8870D-1 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;
the decoder uses digital counting techniques to detect
and decode all 16 DTMF tone pairs into a 4-bit code.

Functional Description
The MT8870D/MT8870D-1 monolithic DTMF receiver offers small size, low power consumption, and high
performance. Its architecture consists of a bandsplit filter section, which separates the high and low group tones,
followed by a digital counting section which verifies the frequency and duration of the received tones before passing
the corresponding code to the output bus.


Onboard complex frequency decoder chip MT8870  

Voice input interface board  

Onboard five LED indicators for easy viewing of the output state  

The chip has been drawn with mainly basic pinouts  

PCB size: 26.5 (mm) x 24.5 (mm)  

Datasheet: https://goo.gl/W43m4S