Found in Popular Electronics from the 1980s, this circuit uses two operational amplifiers from that time. The circuit has frequency and symmetry adjustment.
This 1995 circuit uses interruption sensors or NC connected in series in any quantity. With the...
The integrated circuit used in this amplifier is not common today. The circuit is from a...
This circuit turns off a load after an interval of 8 to 80 seconds adjusted on the potentiometer. The...