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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 76 



later simplified by omitting the wire, spring, etc., and substituting a 

 piece of metal which was prevented from short circuiting the termi- 

 nals of the base by a thin piece of paper. When the lamp burned 

 out the entire 1200 volts was impressed across this piece of paper, 

 puncturing it and so short circuiting the base terminals. Should one 

 or more lamps go out on a circuit, the increase in current above the 

 normal 3 amperes was prevented by an adjustable resistance, or an 

 extra lot of lamps which could be turned on one at a time, connected 

 to each circuit and located in the power station under the control of 

 the operator. This system disappeared from use with the advent of 

 the constant current transformer. 



THE SHUNT BOX SYSTEM FOR SERIES INCANDESCENT LAMPS 



Soon after the commercial development of the alternating current 

 constant potential system, a scheme was developed to permit the use 



'Reactance Coils- 



■ M I 



Consl-ant 

 Voltage . 



Alternating ( 



Corre.ni' y 



Dynamo 



Ky 



a 



Ky 



H 



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Shunt Box System, li 



Lamps were burned in series on a high voltage alternating current, 

 and when a lamp burned out all the current then went through its 

 '' shunt box," a reactance coil in multiple with each lamp. 



of lamps in series on such circuits without the necessity for short 

 circuiting a lamp should it burn out. A reactance, called a " shunt 

 box " and consisting of a coil of wire wound on an iron core, was 

 connected across each lamp. The shunt box consumed but little 

 current while the lamp was burning. Should one lamp go out, the 

 entire current would flow through its shunt box and so maintain the 

 current approximately constant. It had the difficulty, however, that 

 if several lamps went out, the current would be materially increased 

 tending to burn out the remaining lamps on the circuit. This system 

 also disappeared from use with the development of the constant 

 current trans fonner. 



