[neilk]

There are religious proscriptions against doing work on the Sabbath (for Jews, beginning Friday at sundown and lasting until Saturday evening). These include lighting a fire. Some religious authorities believe that completing an electric light is the modern equivalent.

Thus, there is an entire industry of elaborate contraptions to allow the observant Orthodox Jew all of the convenience with none of the covenant-breaking. Like this switch, which doesn't create an electric circuit; it blocks an intermittent light pulse which has some possibility of not even doing anything.

Allegedly this is more acceptable to the Almighty. Perhaps because the Torah lacks an anti-circumvention clause.