MT8870 DTMF Telephone Voice Decoder Module

 

MT8870 DTMF module is connected to the phone via the headphone jack. It detects the sound signals coming from the pressed keys and thus can send commands. You can read 4-bit key information with Q1, Q2, Q3 and Q4 pins, so you can use this product to operate certain products with the keystrokes you make in Arduino projects. The product has dimensions of 26.5mm x 24.5mm. It has a 3.5mm audio input socket.