This circuit is from a 1980s Signetics documentation. The circuit separates the modulation signal from a carrier. The used components are not common today.
This circuit was obtained from an English magazine from 1981. The magazine no longer exists, but...
Radio Electronics published this circuit in a 90's edition. The circuit makes use of an uncommon...
This TTL module can be used in counter and many of them can be cascaded to counts up to 99, 999,...