Robotics is combination of various techniques i.e. Sensing, Controlling and information processing
etc. Our concern here is to replace the human force at the border areas with the portable robots. These robots are
mounted with sensors to detect the presence of Unauthorized persons. The sensor used here is the P.I.R sensor. To
control the robot wirelessly, we use a GSM phone because of the wide coverage of the mobile networks. By making a
simple telephone call, through the signals generated from the DTMF systems, the robots can be controlled. Several
tones are generated from the GSM mobile with different frequencies that identify each key touched in a telephone.
This tone is called „dual-tone-multiple-frequency?(DTMF) tone. The robot perceives this DTMF tone with the help of
the phone stacked on the robot. The received tone is processed by the 89c51 microcontroller with the help of DTMF
decoder. The decoder decodes the DTMF tone into its equivalent binary digit and this binary number is sent to the
microcontroller. The microcontroller is pre-programmed to take a decision for any given input and outputs its
decision tomotor drivers in order to drive the motors for forward or backward motion or a turn. The mobile that
makes a call to the mobile phone stacked in the robot acts as a remote.