Wireless Telegraphy and Telephony

WIRELESS TELEGRAPHY 81 incoming and to the condenser, spark gap and coil when the signals are to be transmitted. Waves coming in from any particular direction produce oscillations in the two aerial circuits whose intensity varies according to the direction in which the waves come. These currents passing through the coils generate a mag- netic field having a direction perpendicular to that from which the waves come. The strength of the currents in Fig. 99.—Complete receiving and transmitting outfit. the movable coil will depend upon its position in the re- sultant magnetic field and will be at a maximum when the coil embraces as many as possible of the lines of magnetic force. By providing the movable coil with a pointer it is pos- sible to thereby determine the plane in which the station producing the signals lies. Any ambiguity regarding the final position of the station, whether it is located in the same direction indicated by the pointer or in the opposite one, is only removed by general knowledge of the location of existing stations. The processes involved in sending messages are the re- verse of those entering into the receiving apparatus. The movable coil being connected with the condenser, gap and