Suggested by General Electric in a 1970 document, this circuit uses a LASCR, or SCR fired by light. This component is uncommon today.
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....