CARBON GRANULES AND TEST JIGS, circa 1970

Laboratory equipment and bottles of Graded Carbon granules used for the development of telephone transmitters. The first item in the middle of the picture, is a Thomson cup (Joseph John Thomson 1856-1940), which is a graphite bowl with a conical cavity divided by an insulating material and connected to two wires, which would lead to an electronic measuring device (known constant current source). We assume that the purpose of which is to determine the best resistance for manufacturing telephone transmitters. The item on the left appears to be for measuring the quantity and quality of carbon. On the right of the picture is a similar system that has two glass funnels, one graduated, and on the right of the frame, difficult to see in the picture is a spike on the base, connected to the frame, above is an insulated bridge with a adjustable threaded thumb bolt. A rod of something like carbon may have been inserted here, purpose unknown.

Donated by John Barnes

A1815