This common circuit with two transistors was found in an old French publication. The supply can be from 5 to 12 V depending on the relay used, or 24 V as in the original, if the relay is for this voltage, and the time depends on the capacitor and the potentiometer setting. The potentiometer can be from 100k to 1Mohm and the capacitor from 1 uF to 2 200 uF.
