This 1968 Mallory circuit uses an uncommon integrated circuit today. The circuit has a 30 to 20,000 Hz response with lower power and is powered by 12 V.
This circuit consists of a simple continuity test with two transistors forming a relaxation...
We found this circuit in a Popular Electronics of the 90s. The circuit uses a touch sensor formed by...
Found in National Semionductor documentation this circuit combines a tone control with an...