Found in the February 1990 Radio Electronics issue, this sophisticated 100 MHz probe uses a period display module. The circuit has an external power supply.
The UAA180 integrated circuit is no longer manufactured, but if the reader finds one in a scrap...
This application circuit for the AD6521C was found in Radio Electronics from the 90's. The circuit...
This interesting capacitive water level sensor was found in Popular Electronics. The circuit can be...