This circuit activates a relay after a time given by C1 and R1. The circuit is from a Radio Electronics from December 1974. The relay voltage is the same as that used in the power supply.
This switching power supply was found in an Electronic Design from the 90s. The components are...
This burglar alarm is highly efficient, depending of course on the care with which it is...
This circuit is from a 1969 Electronics World. The transistors may be modern general-purpose...