Nikola Tesla Books
OSCILLATION TRANSFORMERS 47 joined with a cable which places the two primaries in series. The oscillation circuit is, of course, through both primaries. Still a further modification of this circuit is made by placing the two resonators base to base as shown in Fig. 4. This makes virtually a Tesla coil of the pair, the only distinction being in the grounded neutral point. Advantages of Various Types.-The Tesla coil gives the longest spark between points of any of the various types. This coil is difficult of construction, however, and in mechanical design it is fundamentally poor. The greatest problem is to support the primary and secondary and still prevent leakage of the current. The combined type, Fig. 4, or the style shown in Fig. 3, will overcome this difficulty with but a slight loss in results obtained. The Oudin coil gives an enormous brush discharge from its single terminal. In a large coil, the streamers of purplish fire dart out like the branches of a tree to a distance of several feet in all directions. Such a coil, properly proportioned and carefully built will give splendid results. The construction is simple and the design strong both electrically Fig. 2.-Wiring diagram for Tesla coil showing transformer, spark gap and con denser
