Serial switch with PIN diode (CB21257E)

This circuit was found in a Popular Electronics from the 90's. The circuit is connected in series.

Passive Tone Control (CB19183E)
This circuit appears in several versions on this site. It is designed to be used between the...
Ultrasonic Scarecrow (CB12342E)
This circuit uses a piezoelectric tweeter to emit a powerful continuous sound above the audible...
Touch Lamp Control (CB26132E)
This circuit is based on a Siemens S566B integrated circuit. The circuit is from a Radio...