This simple metronome, from 1985 documentation uses only transistors and has two settings. For voltages above 6 V, up to 12 V, replace the BC557 with a BD136.
This circuit uses an optical coupler to indicate a phone call through a lamp. The circuit is from...
The LM320 is a negative voltage regulator up to 15 V with maximum current of 1 A. In this circuit we...
This circuit was obtained in a 1986 documentation consisting of an active frequency divider for...