experiments to temporarily close an electrical circuit.
It was offered by CENCO in their scientific apparatus catalog.
It is an earlier style than shown in their 1930 catalog
so probably dates from the early 1920s.
experiments to temporarily close an electrical circuit.
It was offered by CENCO in their scientific apparatus catalog.
It is an earlier style than shown in their 1930 catalog
so probably dates from the early 1920s.
