This CMOS 4001 oscillator alternately turns the relay on and off at times set by R2. The circuit is from Electronics Now magazine, June 1995.
The integrated circuit used in this project is not common today, but it can be implemented with more...
Found in an American publication from 1969, this circuit can be adapted to be used as a shield....
This current meter with many scales was found in a 80s American documentation. The operational amplifier...