TELEPHONE, MECHANICAL. 



811 



International Copyright. An international con- 

 ference for the conclusion of a treaty for the 

 protection of literary property was opened on 

 Sept. 6, 1886, under the presidency of the 

 President of the Confederation. Austria-Hun- 

 gary took no part in the conference, because 



changes in the municipal law would be neces- 

 sary before the treaty could be made effective. 

 The United States and Russia were not repre- 

 sented in the conference, for similar reasons. 

 The treaty was concluded, and was formally 

 signed on September 9. 



TASMANIA. See page 64. 



TELEPHONE, MECHANICAL. The principle of 

 the mechanical telephone was known long be- 

 fore that of the magnetic telephone. In its 

 simplest form, the "lover's telegraph " of the 

 old text-books on physics, it consists of two 

 cylindrical boxes, each closed at one end by 

 a tightened membrane, and connected by a 

 string. Each box acts alternately as trans- 

 mitter and receiver, the vibrations being car- 

 ried mechanically from one membrane to the 

 other by means of the string. In later forms of 

 this instrument, designed for permanent use, the 

 membrane has been replaced by a thin sheet- 

 iron diaphragm, and the string by a wire ; but 

 there have always been several drawbacks at- 

 tending its practical use. In the first place, 

 the connecting wire, like the string in the 

 "lover's telegraph," must touch nothing, and 

 therefore could not be carried around corners ; 

 and, in the second place, it must be tight, and 

 therefore either a rise or fall in temperature 

 might stop communication, the former by ex- 

 panding and thus loosening the wire, and the 

 latter by contracting it, and thus creating a 

 strain powerful enough either to break it, or 

 to pull the head from the telephone. Any 

 effort to prevent the latter result, by making 

 the diaphragm thicker and stronger, evidently 

 makes the instrument much less sensitive. 

 Both of these objections have been recently 

 overcome by the devices of George F. Shaver, 

 of Erie, Pa. For carrying the wire around cor- 

 ners, he uses an iron truss made in the shape 

 of a letter W (Fig. 1). The truss is fastened 



Via. I. 



to the corner by a stout rubber loop at A, and 

 the line-wire passes through loops at B, C, and 

 D. The whole truss yields sufficiently to carry 

 the wire around in a curve, with no sudden 

 change of direction, and also accommodates 

 itself to any expansion or contraction of the 

 wire, thus taking the strain off the telephone. 

 The latter is made strong by the manner of 



fastening the line-wire to it. In the old form 

 of the instrument, the wire passes through the 

 diaphragm, and is secured by a ball or a short 

 transverse bar. In the Shaver telephone the 

 wire is not fastened directly to the diaphragm, 

 but is secured to a ring R (Fig. 2). This is 



B 

 A 



FIG. 2. 



connected with the diaphragm by four wires (of 

 which only two are shown" in the illustration), 

 each passing through the diaphragm as at A 

 (Fig. 3), back again as at B, and being again fast- 

 ened to the ring R. Thus the parts of the four 

 wires visible from the front of the diaphragm 

 form the alternate sides A B, C D, E F, and 

 (f H, of an octagon. With these are interlaced 

 four other wires, L B C M, etc., on the front of 

 the diaphragm, secured firmly at L, M, etc., on 

 the frame that sup- 

 ports it. This frame 

 thus bears any sud- 

 den pull that may be 

 given to the line- 

 wire, while the whole 

 system is so closely 

 connected with the 

 diaphragm as to vi- 

 brate readily with it. 

 Very sensitive dia- 

 phragms of the finest 

 silk can thus be 

 used, and, since they 

 are connected with the line- wire at many points 

 instead of but one, this arrangement serves 

 also to intensify the sound. In the perfect in- 

 strument, a cone, with a base slightly smaller 

 than the octagon A, B, C, D, placed in front 

 of the diaphragm, with its apex toward the 

 speaker, serves to distribute the sound to those 

 parts of the diaphragm connected directly with 

 the line-wire. The signaling can be done with 

 the ordinary magneto-bell, or by knocking 

 sharply on the frame of the telephone. 



This form of telephone has been operated 

 over wires two miles in length, and gives ex- 

 cellent results for short private lines. About 

 400 of them are in use in New York city alone. 

 Mr. Shaver has also invented an " exchange," 



FIG. 3. 



