This circuit is from a 1965 General Electric manual. It uses components from the time that admit equivalents. The SCR can be the TIC106 and the LDR of any type.
This is a commercial radio circuit from the 1960s. The circuit was found in a Japanese publication from...
We found this circuit in a 1967 American documentation. The diodes are general-purpose and the...
This beat frequency oscillator or BFO was found in an American 1980s documentation. The circuit is...