This circuit was found in an American documentation from the 90's. What it does is provide at the output a voltage that is the average of the voltages set for the inputs.
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...