The MT8870 based DTMF (Dual Tone Multi-Frequency) decoder module is commonly used to control robots with a mobile phone, it is also used in different kinds of home automation projects where mobile dial pad input is required. This module works as a tone decoder that uses its 3.5 mm audio connector socket to get the input audio signal. It is popularly used for mobile and fixed telephone voice dialing and recording related functions.
 
Features of MT8870 Decoder Module
Power Input: 5V Nominal (4.5V - 5.5V)
Onboard 3.5mm jack input Facility
MT8870 Based Frequency Decoder
5 Channel Interface
Detects 0-9, A-D, *, #
LED notifier for Output state
2.54” Pin pitch
Board Dimension: 37 x 25 x 12 mm (l x w x h)
 
Resources:
1. MT8870 DTMF Decoder Module - Overview
2. MT8870D Data Sheet