This 80's Exar circuit has a carrier detector for frequencies up to 500 kHz. The circuit uses a company 567 which is still a common component.
This circuit is from Motorola documentation from the 70s. The transistors support modern...
We found this shield circuit in a 1991 technical documentation. The phototransistor can be...
This sonic control circuit for a small robot turtle was obtained in an American documentation from 1967....