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 makes use of a PLL 567 and the components must be calculated according to the desired...
The transmitter can be that of CB9574E. This receiver uses a PLL to directly trigger a sensitive relay....
This circuit is from a 1967 US publication. The configuration can serve as a basis for designs...