Vintage Asylum

RE: Good Point

68.103.9.72

In Reply to: RE: Good Point posted by unclestu52 on March 23, 2008 at 16:03:56

The original photo detector was a vacuum tube. Once upon a time in the 1950's automatic doors, alarms, etc were activated via a light beam interuption, as detected by that vacuum tube. Side rails directed pedestrian traffic towards doorways & the end posts contained the light beam emitter & detector, thus allowing the door to be opened just before the pedestian approached it.

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