This circuit is from an American publication of the 80's. It makes use of components of the time. However, the circuit is the basis for a modern shield application since the input is TTL.
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...