GSM controller without microcontroller

If you are not familiar with microcontrollers but you still need some kind of DIY GSM controller, well, this is the thing for you. It consists of some cheap GSM phone that has "handset" port and can be configured to auto-answer incoming call, DTMF decoder (MT8870) and a few controlling relays.

When you call this GSM controller it will establish a voice connection. By pressing on any key on your phone's keypad, GSM controller will receive that DTMF signal and MT8870 circuit will set the appropriate binary value on it's data pins Q4..Q1. Those data pins will turn on or off relays connected to them. In order to expand number of data lines, you should connect SN74LS138 or SN74LS154 integrated circuit that will enable up do 12 relays to be connected and controller.

© unknownpocketnerd

[ Source: unknownpocketnerd ]

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