This circuit provides a 5 V negative output with a maximum current of 1 A. The circuit is from the 1993 Linear Technology Applications and uses common components at the time.
Old phones with dials can be used in a simple home intercom system, as this circuit from Popular...
This circuit recognizes a tone by its frequency triggering a relay. The LC circuit determines the...
This circuit was obtained in a 1980 publication, but it can be easily assembled today, as all...