This circuit controls the channel separation as described in the March 1973 Radio Electronis magazine article. The circuit was proposed by Mullard (Philips) and consists of two channels as shown.
Using components from the era, this 90's EDN circuit is used in analog to digital conversion...
Found in an American publication from the 90s, this circuit allows the supply of 3, 6 and 9 V...
We found this circuit in an old Popular Electronics. The circuit is experimental, driving an LED...