Found in Texas Instruments documentation from the 1980s, this circuit applies to digital signal transmission with FSK modulation. The circuit is slow, as it uses period components.
This SCS counter circuit was found in a 1964 General Electric documentation. The circuit has a...
This simple 1-transistor reflex receiver was published in Radio Electronics magazine in September 1959....
Operational amplifiers used in this 80's circuit is not very common today, but the setting can be...