This circuit was obtained from an American documentation from 1968. The current depends on the operational, observing that the circuit uses a symmetrical power supply.
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....