This Schmitt optical trigger with LDR was found in old documentation. The relay must be sensitive, or an additional step must be used to trigger it.
Found in National Semiconductor documentation from the 1980s, this circuit uses an operational...
This basic voltmeter circuit has an input resistance of 2 M. The instrument is 100 uA and the...
This simple alarm using only transistors was found in a 1990 publication. It can be powered by D...