This circuit appears on this site from different sources. This is from documentation from the 1980s. The operating system used is uncommon and can be replaced by a more modern equivalent.
The CMOS 4046 integrated circuit is not very common today, consisting of a very efficient PLL for...
This configuration with complementary transistors causes an LED to flash at a frequency that is...
This circuit was found in a 1968 documentation. It makes use of both NO and NC reed-switches and small...