This oscillator can generate 2 to 10 MHz signals and was found in an American 1980s documentation. The circuit is stable and its supply voltage is 5 V.
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....