This circuit was found in a 90's Electronic Design. The circuit can be adapted to use modern components. The power supply is made with 5 V which allows its use as a shield sensor.
This circuit is from an English publication of 1991. With it you can use a common multimeter on...
This circuit can be found in a 1970 Motorola documentation. The circuit can be implemented with general...
Delayed Pulse Generator This can be considered an "advanced" application where two 555 integrated...