When we talk about wireless robot vehicles, we usually think about the RF circuits. But this project is different. It uses a mobile phone to control the motion of a robotic vehicle, and therefore, the range of operation is as large as the coverage area of the service provider.
The project is based on an ATmega16 microcontroller that is interfaced to the mobile phone through a MT8870 IC, which is a DTMF to BCD decoder. So how this works is you have to first call the cell phone that is interfaced with the microcontroller from any other phone. The cell phone must be kept on auto-answering mode so that it can receive the incoming call.
Read more: Cellphone controlled robot vehicle using ATmega16 microcontroller