This circuit was obtained in a 1967 Electronics World. The components are still common today, the SCRs can be replaced by equivalents and the unijunction transistors the 2N2646.
Using bipolar, FETs and unijunction this long-lasting timer can reach 10 hours with good quality...
The configuration shown is from the National Semiconductor Linear Applications Handbook. The...
This shield circuit uses a common CMOS port. The voltage depends on the interfaced logic. The...