In this project we can control the devices at homes or industries from our mobile without any contact. For this we are using DTMF [Dual Tone Multi Frequency] technique which is an in built feature to few mobiles. This project is designed in such a way that the Industrial or home devices are interfaced to the microcontroller  through the relays along with one mobile which supports DTMF by using DTMF decoder.
A normal mobile phone will be used as a remote control. A call is established between the controlling mobile and the remote mobile. Now any key pressed on the remote mobile will generate a complex frequency, which can be heard on the mobile placed. That frequency can be detected by controller by means of DTMF decoder. Keys assigned for control can be User Defined. Depending on the keys pressed the micro controller can be programmed in such a way that it can control any devices in homes or industries. This project uses regulated 5V, 500mA power supply. 7805 three terminal voltage regulator is used for voltage regulation. Bridge type full wave rectifier is used to rectify the ac output of secondary of 230/12V step down transformer.