New York Schenectady, N. Y., al- Electllc Company, a corporaappucausn liu-en :1, 1935, seria No. 13,273 ` 170mm. (ci. 171-95) My invention relates to electrical and magnetic indicating, measuring, and controlling methods and devices and concerns particularly arrangements responsive to unidirectional currents or uxes. v An object of my invention'is to provide a sensitive method of detecting the 'pr