The sensor is S1 in this alarm that we found in a Radio Electronics magazine from May 1971. Several sensors can be used in series. The SCR supports equivalents from the 106 series.
This simple MW radio was found in a 1975 publication, but it can be mounted with BC548...
This control for bass, midrange, and treble was found in the March 1995 issue of Electronics Now...
This circuit from a 1967 documentation generates 2.5 Hz signals depending on the capacitors used,...