We found this circuit in an English publication from the 1980s. The circuit uses current components and can be tuned for frequencies between 300 and 1500 Hz.
This basic voltage comparator circuit has a reference voltage given by a zener diode. The input...
This circuit was found in a Popular Electronics documentation from the 90s. It is possible to switch...
This solid-state relay (SSR) or shield was found in a 1995 Electronics Now. The transistor can be...