Found in a 1980s American documentation, this circuit appears with variations elsewhere in this section. The circuit activates a relay according to the supply voltage.
We have in the figure a traditional amplifier configuration with operational amplifier. The source...
This circuit was found in a 1977 Radio Shack documentation. The circuit is TTL, which must be...
This circuit is suitable for modulating small FM transmitters for eavesdropping or espionage. The...