This circuit was found in an ancient American documentation. The power supply is not given, but we have the voltages used. The relay is sensitive type for high voltage.
This alarm circuit is from a 1987 publication, however the components used are still modern. The...
In the figure we have a configuration that allows to test NPN transistors and with the addition of a...
We find this current meter circuit from 0 nA to 200 nA in a Linear Technology application manual....