Switch for Jump Spark-lighting.
In a switch for controlling the current of the secondary coil it will be evident that the utmost attention must be paid to matters of insulation. The object of such a switch is to control a number of circuits; for example, as it is not advisable to put more than 20 to 25 burners on one circuit, a case requiring the lighting of 100 burners would necessitate some means of passing the current to each circuit in turn. This is shown in Fig. 42, in which S is a hard rubber plate, provided with a revolving metal arm and handle, H, and four contact points, P, which latter receive the ends of the wires from the groups of burner condensers B by means of nuts or binding posts. The wire from the secondary of the coil is run to the switch-handle, H, great care being taken that it does not pass near to the circuit wires, or contact points. Revolving the switch-handle connects the secondary wire to each circuit in turn. It will be noticed that, unlike a battery switch, this one has a large base, long switch-arm, contact points situated far apart, and every precaution taken to control the passage of the high-tension current. The base should always be of rubber or glass. Shellacked-wood, or such substitutes, are productive of trouble.
Fig. 42.
When it is desired to light automatically a number of burners from a distance, the Trailer (Fig. 43), is used. This is a switch similar to above, but the arm is revolved by means of toothed wheels by the electro-magnet shown on the back. As it is never desirable to unnecessarily prolong the secondary wires, this device admits of the switch being put near the circuits, and yet being operated from afar.
Fig. 43.