This circuit was found in an 80's Poptronics. The circuit is a fast trigger whose signal can be taken from the Q2 collector. The supply can be done with voltages from 9 to 12 V.
This adding amplifier with the operational LM324 is from the SGS integrated circuits manual of...
This circuit measures the conductivity of a saline solution, which is affected by the electrolysis effect....
This circuit activates one of the selected circuits with a touch of a switch, keeping it...