This basic Schmitt trigger was found in an American publication from 1968. The circuit uses transistors from the time. Modern general-purpose types can be used.
We found this circuit in a 1976 documentation. The FET can be the BF245 and the bipolar transistor a...
This circuit is the receiver for the CB13997E. The transistor can be the BC548. We also found this...
We found this oscillator in a publication for radio amateurs from the 70s. The circuit generates...