Page:US Patent 755840 (Bose's Microwave Apparatus).djvu/2

 No. 755,840.

To all whom it may concern:

Be it known that I,, a subject of the King of Great Britain and Emperor of India, and a resident of Calcutta, India, have invented certain new and useful Improvements in or Relating to Detectors for Electrical Disturbances or other Radiations and in Electrical Resistances, of which the following is a specification.

This invention has reference to detectors and so-called "coherers" for the reception of electrical disturbances, Hertzian waves, light-waves, and other radiations; and its object is to further improve the sensitiveness and quickness of response of devices of the kind in question.

According to my theory, upon which the invention is based, the changes produced on or in the sensitive substance of a coherer or detector by electrical disturbances, Hertzian waves, light-waves, and other radiations are due to molecular distortion. In order to obtain the best results with a detector or coherer, it is necessary that this distortion shall be removed before the detector or coherer receives fresh radiations—as, for example, the signals in wireless or other telegraphy.

In order to restore the quickness of response of coherers and detectors in actual practice, it is usual to resort to tapping contrivances; but this expedient besides being crude in conception involves expense in construction, complication of apparatus, and must necessarily be slow in action and somewhat spasmodic. According to the present invention I effect this object by subjecting the sensitive substance of a coherer or detector to certain methods, influences, or agencies which will have the effect of removing this distortion, thus hastening the recovery of the substance. For instance, I may subject the sensitive substance to torsional distortion by imparting to the tube or medium containing or carrying the sensitive substance—such, for example, as iron or other filings—either a one-directioned or an oscillatory or vibrational twist. In order that this may be conveniently accomplished, I may place the substance in an elastic tube or elastic medium, the elastic tube or medium having the effect of facilitating the action of the twist upon the sensitive substance and of insuring quick recovery, or with the same object of increasing the sensitiveness and quickness of self-recovery of the sensitive substance I may subject the mass forming the receiver to certain forces, physical surroundings, and conditions suitably adjusted and applied, whereby said mass becomes more responsive to electric disturbances, including Hertzian waves or other forms of radiance. For example, I may produce this effect: (a) by annealing or by mechanical treatment; (b) by heat; (c) by subjecting the substance to increase or reduction of pressure; (d) by subjecting the substance to vapors or gases ordinarily applied—for example, by inclosing the substance in an atmosphere of gases or vapors—for instance, ammonia-vapor or carbonic-acid gas; (e) by the occlusion of gases in the sensitive substance; (f) by surrounding it with various gaseous fluids—for example, NH$3$ or CO$2$; (g) by proper adjustment of pressure by means of a micrometer-screw or other means till the critical point is approached; (h) by creating a partial vacuum in the receptacle in which the sensitive substance is inclosed and adjusting the vacuum until the critical point is reached.

Further, as the response of a detector or coherer is due to distortion, I may according to one part of my invention increase the facility of response of the sensitive substance by allowing various agencies to produce a tendency toward distortion on the verge of signaling or reception of the radiation, the radiation itself precipitating the change.

According to another way of carrying the first part of the invention into effect I may dispense with mechanical means for producing recovery of the coherer or detector by using sensitive substances in which the recovery is automatic.

I have discovered that substances of a certain class possess the property of self-recovery—namely, those which give a characteristic curve representing relative resistances. With such substances if the relation between a continuously-increasing electromotive force and the resulting current be represented by a