
Louder music, sirens or speech in response to higher ambient noise
levels? This simple circuit has the answer, and it may enable your robot
to be at least as noisy or loud-mouthed as the others in an arena. The
circuit consists basically of a microphone, a level detector, a 4-state
counter and four analogue switches connected to a resistive ladder
network. Looking at the circuit diagram, the signal from electret
microphone M1 is amplified by...