Nikola Tesla U.S. Patent 725,605 - System of Signaling Patent Wrapper Page 79

J acter, of a receiving apparatus comprising a plurality of circuits each tuned to the impulses of one kind emitted by the secondary of the transmitting transformer, and a receiver dependent for operation upon the conjoint action of the receiving circuits, as set forth. 13. In a system for the transmission of electrical energy, the combination with a transmitting apparatus comprising a transformer and means for impressing upon the secondary elements of the same oscillations or impulses of different periodicities and in a given order of succession, of a receiving apparatus comprising a plurality of circuits each tuned to respond to the transmitted impulses of one period, and a receiver dependent for operation upon the conjoint action of the receiving circuits, as set forth. 14. In a signalling system, the combination of means for generating a series of electrical impulses of different periodicities, receivcing circuits of differing electrical periods of vibration, and an indicating mechanism operated to give an intelligible indication only when currents are induced in the receiving circuits in a predetermined order, as set forth. 15. In a system for the transmission of energy, the combination of two or more circuits differing with respect of one of their electrical constants, means for energizing said. circuits, and an indicating mechanism operative only by conjoint action of two or more currents generated by waves from the sending station, as set forth. 15. In a system for the transmission of electrical energy, the combination with a transmitter adapted to produce electrical waves or oscillations varying in character in a 693