Variable Frequency Tone Generator

Figure 1.  Circuit Diagram for Variable Tone Generator

This is a circuit for a generating a variable tone.  The main component of this circuit is the 555 timer IC, configured as an astable multivibrator.  A 555 configured as such outputs a periodic signal with a frequency determined by the values of R1, R2, and C1.

By feeding this 555 output to a speaker as shown in Figure 1, a tone will be produced, the pitch of which depends on the 555 output frequency. The tone generated by this circuit is adjusted by varying the value of potentiometer R1.