Nikola Tesla U.S. Patent 725,605 - System of Signaling Patent Wrapper Page 25

J J 1 T 1 1 to the slightest disturbing influence. Its return to the hormal sensitive state may be secured by momentarily interrupting the battery circuit after each operation, or otherwise. The relays R1 R² have armatures 112, which are connected by a wire w, and when attracted, establish electrical contacts at land, thus closing a circuit containing a battery b3, an adjustable resistance and a relay R3. From the above description it will be readily seen that the relay R3 will be operated only when both contacts and ² are closed. The two vibrations at the sending station may be controlled in any suitable manner, as, for instance, by opening or closing the circuit of the source S, electrical vioretions being sent out simultaneously or in rapid succession, as may be desired, at each closure of the circuit. The two receiving circuits at the distant station, each responding to the vibrations produced by one of the elements of the transmitter, affect the sensitive devices a¹ and a² and cause the relays R¹ and R to be operated and contacts and closed, thus actuating the receiver or relay R³, which in turn establishes a contact c3 and brings into action a device a³ by means of a battery b4 included in a local circuit, as shown. But evidently, if through any extraneous disturbance only one of the circuits at the receiving station is affected, the relay R³ will fail to respond. In this way communication may be carried on with much increased safety, and entire privacy of the message may be secured. The receiving station shown in Fig. 2 is supposed to be one requiring no return message, but if the use of the system is such that this is necessary, then the -7639