We found this circuit in a 1967 General Electric SCR manual. The time is set to R1 and depends on C1 which must be a low-leak capacitor.
This circuit was found in a 1980s Intersil documentation. The integrated circuit used is not...
Although it is a common configuration today, these circuits were taken from an old publication. The...
This circuit, from an old publication, can also use modern transistors. Note that the unit is...