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A Valve Detector is not an instrument for detecting valves, but a Detector module for reception, using a valve (a radio tube, an evacuated glass envelope with a diode function). This one comes with a crank on the side that looks like an automotive starting crank, but is just a control on an external rheostat for controlling voltage and current. Size not indicated, but figure those terminal points are about a quarter of an inch across for starters. Published in the August, 1913 issue of MODERN ELECTRICS.
Source: Magazine collector Steve Davis
Restoration by: magscanner
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