Robo India in this PPT presents the working principles, concept and usages of Dual Tone Multi Frequency Signaling -DTMF. It also exhibit how to use DTMF with AVR series microcontrollers like Atmel Atmega 16, Atmega 8, Atmega 32 etc. We welcome all of your views and queries, we are found at- website: http://roboindia.com mail- info@roboindia.com