Signedon cover: THE LEEDS & NORTHRUP CO. / PHILADELPHIA
Inscribedon cover: E331 [faintly etched on top of] E342
on side, painted: E342 / Resistance Box / 1-400
FunctionSuch an instrument is used to measure the resistance of electric conductors. For a short general description and other images, go to the following website.
The series of brass blocks are connected to one another with the coils underneath. When the plugs are all in, the resistance is negligible. When one or more plugs are removed, the resistance of that or these plugs are introduced into the electric current passing through the box.