MT8870 DTMF Audio/Speech Decoding Telephone Module

This component is ideally suited to adding dual tone multi-frequency (DTMF) decoding to your project. This detection module interprets the incoming tone and produces a coded output that can be connected to all manner of microcontrollers.

DTMF is commonly found in touch tone devices such as a phone. The tone is a combination of two separate sine waves that produce a unique signal that can be transmitted or heard. When the module receives the signal it is able to decode it and produce a binary output that can be used in other devices. The module shows the state of the signal through onboard LEDs.

As an idea, you can connect up a mobile phone via 3.5mm to 3.5mm cable to the module. Dialling into the phone from a second mobile and then using the keypad will produce the tones on the original phone. The tones in the call can then be interpreted by the module, allowing you to control all manner of projects. The pins are suited to standard sockets with a pin pitch of 2.54mm.

The MT8870 Tone Decoder is a kind of commonly used multi-frequency decode IC product developed by the MITEL company. It is a complete DTMF receiver. After it received the DTMF signal, it will divide the signal into high-frequency group and low-frequency group and send the signal to the digital decoder which can figure out the key value then send it to the outside Bus via four lines( Q1, Q2, Q3, Q4) as the binary form.