Found elsewhere in this section, but from other sources, this circuit is from a 1964 Electronic Design. The transistor is from the era and the power voltage depends on this component.
Found in a Popular Electronics from 1992, this circuit uses a PLL567 in an audio meter bridge that...
We found this circuit in an American 1980s documentation, but it can be implemented with modern...
This BFO or OFB for listening to SSB (Single Sideband) signals was found in the January 1996 issue...