This simple circuit with two transistors was found in a 1985 publication. The power can come from batteries or battery, as consumption is very low.
As monostable we have a proximity switch that can be used as a shield, since the capacitance of...
This circuit was obtained from a 1998s Popular Electronics. The magazine no longer exists, but the...
This circuit was found in the 1972 RCA Power Transistor Databook. Transistors can be replaced by...