This high voltage circuit was found in a 1970 documentation. The integrated one is of the time and modern equivalents can be tested. The resistors of the voltage reducing system must be calculated.
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....