The tone generator’s function is to produce different frequency sine wave for each digital word applied to its input. This project allows the computer to sweep [[wysiwyg_imageupload::]]the instrument under test through the desired frequency range. It can be adapted to create a Morse code circuit, by adding a switch to the output. The circuit here is based upon 555 as a free running multivibrator.  The project is based on 555 timers, working as a free running oscillator. The frequency or pitch of the tone is set by the resistors and capacitors situated in the left side of the circuit. The capacitor is used to reduce noise or undesired signals for smooth operation of potentiometer.Read more to find out how the circuit is constructed and how it works.