This circuit was found in documentation from the 1970s. It eliminates contact bouncing, providing a single pulse. PUT is not a common component today.
This 1967 Raytheon circuit uses an optical coupler of the era and has a range of 800 to 200 Hz....
This interesting digital counter with relays with complementary outputs was found in the Radio...
This circuit uses a diode as a radiation sensor. The operational ones are old because the...