This 40-second delay switch was found in a 1965 Electronic Design. The unijunction transistor might be the 2N2646 and the SCR a sensitive modern equivalent.
This is basically the same circuit as the previous one, but using PNP transistors. In the original...
Found in Popular Electronics from the 90s, this circuit can generate signals from 1 to 10 MHz...
This circuit was found in the July 1992 issue of Radio Electronics magazine. The circuit has a...