High Frequency Apparatus Page 14

14 HIGH FREQUENCY APPARATUS sands of times per second, the discharge gradually dying down until the potential across the condenser has been lowered to such an extent that the spark can no longer jump the air gap. The Condenser immediately takes a fresh charge from the transformer and the entire cycle of operations is repeated. It will be understood that all of this passes in an infinitesimal fraction of a second, the charge and discharge of the condenser taking place so rapidly that the observer can detect no change in the solid spark which appears continuously to fill the gap. As the current surges back and forth through the in ductance, which is merely a coil of a few turns of very heavy wire, a similar current is induced in a second coil of wire placed in the same plane as the first. A slight increase in the number of turns in the secondary over those in the primary will result in a very large increase of potential between the secondary terminals. Unlike the low frequency or commercial transformer the high frequency or oscillation transformer requires no iron core whatever; indeed, the presence of iron in the center of the windings is not to be considered as it would be detri mental to the successful operation of the transformer. From this the reader will note that in order to produce a high frequency current of practically any desired potential, it is only necessary to combine two coils of insulated wire of the proper proportions and number of turns with a con ventional transformer, condenser and spark gap. The Kicking Coil Method.-The operation of a high tension transformer for the charging of a condenser neces sitates an alternating current. There are certain cases wherein it is desirable to produce a high frequency current where direct current only is available. This is particularly true in the case of electro-medical apparatus which must frequently be used at the patient's bedside. For this type