CH. Ill] 



ARC LAMPS WITH SMALL CURRENTS 



are then inserted into the binding posts of the rheostat (fig. 45). 

 This puts the rheostat along one supply wire (in series) . 



The cut ends of the cable are then connected with the binding 

 posts of the arc lamp (fig. 45). For polarity see 701. 



129. Rheostat or other balancing device. As with the arc 

 lamp for heavy currents, those to be used on the house circuit must 

 also have a balancing device of some sort like a rheostat. It must 

 be in one wire (fig. 45). 



Never try to use an arc lamp on any circuit without a rheostat 

 or other balancing device. If one is not used the fuses will be 

 burned out. 



FIG. 44. REICHERT'S AUTOMATIC ARC LAMP FOR USE ox THE HOUSE 

 LIGHTING SYSTEM IF DIRECT CURRENT is AVAILABLE. 



At the bottom are screws for fine adjustment, laterally or vertically. 



128a. In modern wiring for incandescent lamps each group of not over 

 1 6, or in special cases not over 32, lamp sockets must be protected by a fuse 

 or cut-out. The wire must be equivalent to a copper wire No. 14 or No. 18 

 B. & S. gauge, and the fuse or cut-out must be for not over 10 amperes (usually 

 6 amperes) for a 1 10 volt circuit. This is sufficient for the small arc lamp. 



In the older constructions where only one to three lamps were on a single 

 line, very weak fuses were used which would melt if over two or three amperes 

 were drawn from the line. Naturally, on a house circuit thus wired and fused, 

 the fuses would be burned out if one tried to use the small arc lamp upon it, for 

 that rarely draws less than four amperes and often as many as six. 



In using the arc lamp on the house circuit it is therefore necessary to make 

 sure that the wiring and fuses arc of sufficient capacity for the current needed. 



