This simple SCR delay circuit for activating a relay was found in documentation from the 1980s. The components used are common today.
In the figure we have a typical polarization circuit for MOSFETs with a high impedance...
This solar cell powered circuit generates a standard 100 kHz signal. The circuit is from a 1960...
This circuit was found in a 1967 Ferranti documentation. It takes the transistor to the conduction...