MT8870 DTMF Decoder Module
Now available from PMD Way is this useful MT8870 DTMF Decoder Module. The MT8870 IC can decode the DTMF tones generated by a telephone keypad ... with each tone controlling a digital output on the board.
The board is fully assembled, and has a 3.5mm stereo jack socket for audio input. Inline header pins are soldered with which you can connect power and access the digital outputs.
The outputs are BCD (Binary Coded Decimal) so only four pins are required for 16 outputs. (16? Yes... 1 2 3 4 5 6 7 8 9 0 * # A B C D ... however a lot of keypads don't have ABCD). Onboard LEDs also relay the output status for easy testing and debugging.
Click here for a module that has decimal outputs (i.e. real 16 pins for outputs)
How on earth does this be used?
You need a cellular or wired telephone that can automatically answer a call, and hang up once the originator has ended the call. Connect a 3.5mm stereo jack cable from the phone's earpiece to the MT8870 module.
Now call the setup's phone from contemporary telephone. When the setup phone answers, you can press numbers on your phone, which will turn the outputs on and off. Check the tutorial link below for a demonstration.