This circuit can be used with motors or resistive loads, such as heaters and incandescent lamps. The circuit is from Popular Electronics from the 90s. All components used are common.
This fast trigger circuit allows the counting of up to 300 pulses per minute. The circuit is from...
This intercom uses transistors from the 60s. It was found in a Japanese publication at the time....
This circuit is from an old publication from the 90s, but it can be adapted to operate with LEDs....