Exp. 16d Fig. 16-18 from Make Electronics 3rd Ed.
Background: Left 555 Timer (LT) is in astable mode and its output is linked to a speaker (represented by the 8 ohm resistor). The 555 timer on right (RT)) is supposed to control LT. The control pin of the LT is linked to the output of RT.
There are 3 Potentiometers:
P1 on bottom L controls the pitch of the tone generated by LT;
P2 around middle adjusts the frequency and speed of modulation in the control pin of timer LT. If turn P2 down = vibrato sound; if turn P2 up, alarm sound;
P3 on bottom R controls the speed of modulation of timer RT.
