In a DTMF controlled bot, we use DTMF for sending the control signals along the telephone line, to control the movements of our robot. ABOUT DTMFIt is system which consists of two frequencies superimposed. DTMF signals are the superposition of 2 sine waves with different frequencies. Individual frequencies are chosen such that it is easy to design filters and easy to transmit the tones through a telephone line having bandwidth of approximately 3.5 kHz. DTMF was designed to be able to send the codes using microphone. GENERATING DTMFDTMF signals can be generated through dedicated ICs or by using RC networks connected to a microprocessor.MT8880 is an example of a dedicated IC. But getting the latter method work is a bit difficult if high accuracy is needed. The crystal frequency needs to be sacrificed for a nonstandard cycle length. Hence this method is used for simple applications. Most often, DTMF encoder software in PC or inbuilt dialing pulse of landline/mobile can be used for encoding purpose of generating DTMF signals.DECODING DTMF (CM8870 IC)Detecting DTMF with satisfactory precision is a hard thing. Often, a dedicated IC such as CM8870 is used for this purpose.The CM-8870 is a full DTMF Receiver that integrates both band split filter and decoder functions into a single18-pin DIP or SOIC package.Its decoder uses digital counting techniques to detect and decode all 16 DTMF tone pairs into a 4-bit code. HOW TO USE CM8870 IN OUR PROJECTThe output coming at the Q1,Q2,Q3,Q4 digital (i.e. in the form of or 1).We connect these pins to the microcontroller. We take output at these as input the microcontroller unit. Based on the input, we use microcontroller to control the motion of the motors attached to our robot using a motor driving IC like L293D.u00a0