This circuit that imitates the sound of the cowboys' calls with their “louder” was found in a Hands On Electronics from the 80's. The integrated circuits used are from that time.
This is the simulation of a Ultrasound Receiver using the 741 IC, an operational amplifier....
Connected to the output of a small amplifier or receiver, this circuit triggers a relay in the...
We found this powerful transistor amplifier in a 1971 documentation. Output transistors are epoch...