This circuit, which can be used to indicate the movement of an object, was found in NASA documentation. The circuit uses a sensor made with liquid in a container as shown in the figure.
This indicator or VU meter for stereo amplifiers was found in a 90s Radio Electronics. The...
This interesting circuit from 1967 documentation uses three series lamps to regulate the voltage...
This circuit causes an instrument needle to oscillate to signal an event. The circuit is powered by...