Wireless Telegraphy and Telephony

WIRELESS TELEGRAPHY 35 for the mechanical type. One pole of the current is con- nected to a lead plate placed in a jar containing a mixture of sulphuric acid and water. The other side of the cur- rent is connected to a platinum wire placed in a porcelain tube so that only a small part of the lower end is in contact with the solution. When the current passes a bubble forms at the end of the wire shielding it from the liquid, and thus interrupting the current. The bubble is almost im- Fig. 39.—Open and closed core transformers. mediately discharged however and the current allowed to flow an instant before a new one forms. This operation is repeated continuously at a frequency sometimes as high as a thousand per second. An electrolytic interrupter is both an expensive and a troublesome device. There are other types of interrupters of value in wireless service but the limitations of space prohibit any account. The transformer is acknowledged to be the best prac- tice as a means of stepping up the voltage of a circuit for wireless telegraph purposes. Alternating current is nec- essary to operate a transformer. There are two distinct types of transformers known as the “open” and “closed core” accordingly as the shape of the latter is straight like that of an induction coil or in the form of a hollow rec- tangle. The closed core transformer consists of two coils