We found this circuit in a Texas Instruments documentation from the 80s. The circuit uses simple power source and the frequency depends on C1 and R1 basically.
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....