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 from a June 1957 Radio Electgronics is for oscilloscopes of the time with a maximum...
This circuit is from an English magazine Radio and Electronics Constructor of November 1978. The...
This circuit was obtained from a Linear Technology manual from the 90's. The integrated circuits are...