Page:Wireless Telegraphy and Telephony (1908, Massey and Underhill).djvu/41

This, in one of its simplest forms, comprises two blocks of carbon with sharp edges, across which rests a steel needle. This type is illustrated in Fig. 11, and its simplest connections are shown in Fig. 12. The steel needle resting across the carbon blocks forms an imperfect contact. When the high-frequency oscillations pass through the carbons and the needle, the contact is greatly improved,

Fig. 14.—Connections of Electrolytic Detector.

with the result that the local battery current will be strengthened in nearly direct ratio to the improved contact. This change of current causes a sound in the telephone receiver.

Another type used in connection with the telephone receiver is called the Electrolytic Detector. This consists of a small cup containing nitric or other acid, into which the end of a very fine platinum wire is slightly immersed. Fig. 14 shows the principle. It will be observed that the