This circuit was found in an ancient American documentation. The power supply is not given, but we have the voltages used. The relay is sensitive type for high voltage.
We found this circuit in an English documentation from the 60s. The integrated circuits are the...
This circuit was found in a 90s Popular Electronics. It generates tones given by the oscillators and...
This amplifier circuit applies its signal to an ordinary audio amplifier to pick up signals from a...