This project based on DTMF (Dual Tone multi frequency) which is generated in cellular phones. Here, by using a cell phone we controls the home appliances from anywhere in the world (In Network Area). Below you can see the diagram of DTMF keypad. When we press any key then it generates a frequency after mixing two frequencies. And then send it to the receiver end over communication channel.
Fig.1: DTMF keypad
User can activate their devices using this DTMF keypad as he/she want to activate. The encoder encodes the user input and sends via a communication channel. The receiver receives the modulated signal and demodulates it and the user input. In this system, we are going to make a DTMF based home/office appliance. Block diagram of this system given below-
Fig.2: Block diagram circuit
Fig.3 Block diagram of system processes
This system is designed for controlling the devices, it includes a cell phone which is connect to the system via head set. To active the cellular phone part of the system a call is to be made and as the call is answered, in response the user would enter a three/four(as he/she want) digit password to access the system to control devices. As the caller press the specific password, it results in turning ON or OFF specific device. The device switching is achieved by Relays.