This circuit with a bargraph scale was found in a 90s Popular Electronics. The circuit measures the intensity of a sound in three scales. R14 works as a sensitivity adjustment.
This 25 W phase photo control was found in a 1965 General Electric publication. The circuit uses a...
The circuit below uses common JFET transistors, which can be the BF245 or MPF102 amplifying video...
This circuit was found in a 1997 documentation. It works as a booster for VHF and UHF signals...