This powerful sound emitter used in defense to intimidate people was found in a 90s Popular Electronics. The circuit produces a strong modulated tone of 3 kHz. The modulation is 10 Hz.
We found this circuit in a 1967 Electronics World. The circuit can be designed to control other...
The presented circuit monitors a line indicating if it is busy if there is an extension. The...
This circuit is from old documentation. The operational amplifier is uncommon nowadays. The...