Pressing and releasing S, the capacitor C1 charges and discharge slowly through the oscillator producind a changing tone in the loudspeaker. P1 adjusts the discharge time and the tone change. The circuit can be powered from a 5 to 6 V supply when using the BC558, must can source higher power when using a BD136 and powered from a 9 to 12 V supply. In this case the transistor must be mounted on a heatsink.
