400 



MOVING PICTURE APPARATUS 



[On. XI 



"current saver" is sometimes used as a ballast with direct current 

 and effects a considerable saving of power especially when the 

 supply is 220 or 500 volts. (See Ch. XIII, 744). 



When the supply is alternating current the ballast may be in the 

 form of a rheostat but reasons of economy exclude this form of 

 ballast when the machine is used continuously. For continuous 

 performance an inductor (choke-coil), a special transformer, a 

 mercury arc rectifier or a motor-generator is used. (See Ch. XIII, 

 682-683, 72 



FIG. 221. EDISON KINETOSCOPE, PROVIDED 



WITH TWO-WING OUTSIDE SHUTTER. 

 (Cut loaned by the Edison Manufacturing Company). 



When power is independently generated, a special dynamo can 

 be connected directly to the arc lamp without ballast, the dynamo 

 will be its own regulating device. (See Ch. XIII, 680). 



Whatever form of ballast is used, the quality and workmanship 

 should be of the best or an endless amount of trouble may be 

 expected. The rheostat or other ballast must conform to the 

 underwriters regulations and must be satisfactory to the company 



