Counter built by General Electric Co. consists of photoelectric cell installed in box near roadway, on which shines electric light located in ceiling of tunnel; as vehicle crosses beam of light, current is caused to flow; low-energy relay operates counter which records number of impulses and consists of photoelectric cars.
Photo-electric cell counts traffic in Holland tube
Eng. Contracting
Engineering and Contracting ; 68 , n 5
1929
Article (Journal)
English
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