The Secondary Coil.—The fine wire wrapping represents the secondary coil, which is raised to a high voltage, and this actuates the sparking mechanism.
In the art it is customary to illustrate the various contrivances by certain conventional forms. [Fig. 51] shows the manner of designating an induction coil in a diagram, in which the heavy zig-zag line indicates the primary, and the lighter zig-zag lines the secondary coil.
Contact Maker.—A simple little device used in the primary circuit of an induction coil, is known as a contact maker. This, as shown in [Fig. 52], is merely a case A, through which is a shaft B that carries within the shell a cam C. A spring finger D has its free end normally bearing against the cam, and when the nose on the cam moves out the spring finger, the latter is moved outwardly so it contacts with a plug E in the side wall of the case, although it is insulated therefrom. This contact establishes a current through the plug, spring finger and case.
The diagram, [Fig. 53], illustrates the principles of construction and arrangement of a high tension jump spark ignition, in which the electrical source is a battery actuating an induction coil.
High Tension With Battery and Coil.—The battery A has one side connected up by wire B with one terminal of the primary C in the induction coil, and the other side of the battery has a wire D leading to the contact maker. A switch E is placed in the line of this wire.