| 摘要 |
A device for photoelectrically starting and stopping the operation of a bunsen burner in response to the shadow of an operator's hand holding an object to be heated includes a solenoid valve in a line supplying gas to the burner and electronic control circuitry having secondary and primary photoelectric cells arranged in a differential response circuit. Changes in the intensity of the ambient light are cancelled by the differential response circuit, while a hand shadow, which affects only the primary cell, triggers the solenoid valve, via a gate circuit and solenoid switch.
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