This circuit uses a resonant reed relay to recognize the frequency of an input signal. Adaptations can be made to obtain functioning as a shield. The circuit is from 1965 documentation.
This circuit indicates a digital value through a moving bar. The circuit is TTL and must be...
This circuit was found in an Electronic Engineering of the 80s. The circuit indicates when a...
This configuration is from an old Motorola publication from the 70s. In it we have the way to...