Nikola Tesla Books
110 HIGH FREQUENCY APPARATUS has occurred in connection with this type of apparatus and that was caused through the playful antics of a pet dog. The control switch of the outfit was temporarily mounted upon the floor and the canine came bouncing along just as a connection on the rotary spark gap was being changed; a swish of the dog's tail and the switch came down, turning on the low frequency, high potential current. The shock was sickening but fortunately the body was well insulated from ground as the floor happened to be dry. It is the totally unexpected incidents of this nature that develop into real accidents. The high potential current is something that need not be feared, but it should certainly be respected. The Condenser.-The oscillation condenser for this type of apparatus may well be built up into sections of .01 mfd. each as described in former chapters. The total capacity required will range from .04 to .08 mfd., depending upon the number of turns in the primary of the oscillation transformer and the type of quenched gap employed. As the potential is low, the condenser is not subjected to the strains that have to be borne by the usual type. The current is relatively large, however, and the plates are likely to heat if the operation is maintained for any great length of time. For all ordinary purposes of demonstration apparatus, the single units connected in parallel to give the desired capacity will answer but if the coil is to be operated for say half an hour steadily at a time, as is the case in certain branches of electro-therapeutics, the series-multiple connection, in which four times the number of untis are employed, should be used. For detailed directions covering this condenser, refer to Chapter IV which explains the various methods of connection.
