A 'SAVINGS BANK' FOR LIGHT AIDS PICTURE REPRODUCTION
Photo Electric Cells
October 8, 1939
The totalux, developed by General Electric engineers to permit exact time exposures [Subtitle:] Light 'Bank' Designed To Improve Pictures
Better pictures for newspapers, magazines and books as well as better blueprints for engineers will be made possible by the use of an instrument which virtually saves light's beams and puts them in a "bank" until the proper amount has been accumulated, and then closes the account.
This device, called the "totalux," has been developed by the General Electric engineers and is expected to be particularly valuable in photo-engraving, lithography and blue-printing.
The device consists essentially of a photo-electric cell, an integrating device which adds up the variable amounts of light received and a relay which opens a circuit. It is operated by a 90-volt direct current obtained through a rectifier from the alternating current mains.
The photo-electric cell is placed near the original picture that is being copied and in front of the arc light that supplies the illumination for the process.
At the present time exposures are made on a time scale, but this is far from a perfect arrangement when the source of light is variable, as is the case with even the best of arc lights.
The new meter takes account of the variations, adds up the total
amount received, and when the full required amount has been received
its relay shuts off the arc lights and sounds an alarm.
Original Caption by Science Service