Nikola Tesla U.S. Patent 725,605 - System of Signaling Patent Wrapper Page 59

( ( ) ( ( J ( ] Replying to the requirements of the Examiner that certain statements be eliminated from the specification, we beg to say that from the first we have endeavored to set forth clearly but concisely the manner in which this invention may be used to insure both privacy and safety from extraneous interference, and we believe the specification is sufficiently explicit, although the examiner seems to find it wanting as regards the first feature. There are a number of ways by which any desired degree. of privacy may be secured, several of which we will explain somewhat in detail. he indeSince the number of the co-operative elements may finitely increased, privacy could be thus secured without resorting to any other expedient. For it is evident that if the total energy transmitted be divided into a considerable number of series of impul ses, only an instrument of extreme delicacy That is, could be operated by, or "pick up" one of the series. while the proper receiver is actuated by the energy of all the cooperative impulses, the intercepting receiver could be brought into action only by one, or at most by comparatively few, of the impulses, and to intercept a message a degree of delicacy practically unattainable would therefore he required. But with the apparatus illustrated privacy may be attained in a variety of wayswithout increasing the number of circuits, as, for example, by arbitrarily varying the periods of vibration of either of the transmitting elements. Bearing on this, we may quote from page 8, lines 22 to 27: "Instead of closing and opening the circuit of the source S, as before indicated, for the purpose of sending distinct signals, it may be convenient to merely alter the period of either of the transmitting circuits arbitrarily, as by varying the inductance of the primaries." -3673