We find this circuit in a 1980s Linear Technology documentation. The circuit can be implemented on the basis of more modern equivalent components.
Relays from 20 mA to 200 mA can be driven by this sensitive circuit.6 or 12 V relays can be used...
This is a conventional double T oscillator, where the frequency is determined by the double T...
This circuit can be used to recognize a tone by its frequency. When this tone is present in a...