Nikola Tesla Patents
230 the greatest practicable distance, thus extending the range and usefulness of my invention. A great variety of electrical and other devices, more or less suitable for the purpose of detecting and utilizing feeble actions, are now well known to scientific men and artisans, and need not be all enumerated here. Confining myself merely to the electrical as the most practicable of should not this be canch such means, the by far most sensitive device of this kind of which I have knowledge, is a form of luminous discharge which is produced in an exhausted globe under peculiar conditions described by me, and which I have designated as the rotating brush. This discharge is affected by the minute st variations of electrostatic potential or magnetic condition of bodies in its vicinity and may be utilized in a number of ways, as will easily suggest themselves to electricians, for the purposes here contemplated. Another such contrivancè, less sensitive but more readily available, which has been since long ago known and used as lightning arrester, in connection with telephone switchboards for operating annunciators and like devices, comprises a battery the poles of which are connected to two conducting terminals separated by a minute thickness of dielectric. The electro-motive force of the battery should be such as to strain the thin dielectric layer very nearly to the point of breaking down, in order to increas e the sensitiveness. When an electrical disturbance.reaches a circuit so arranged and adjusted, additional strain is. put upon the insulating film which gives way and allows the passage of a current, which can be utilized to operate any form of circuit controlling apparatus. (6)
