Crystal Palace International Electric Exhibition 1881-82

19 [24.] COLLECTION OF RELAYS. a. 1868. Andrews’ Relay for Hughes’ type-printing instru- ment, used by the United Kingdom Telegraph. Company. Its peculiarity consists in the relayed currents being of equal length and independent of the length, of the line current. b. 1858. Whitehouse’s Relay. In this relay a small permanent horseshoe magnet oscillates between the pole pieces of an electro- magnet. The adjustment is effected by the attraction of another small permanent magnet, instead of the spiral spring generally used. c. 1856. Varley’s Horizontal Relay. A. horizontal bar of soft iron is pivoted vertically and free to move in the interior of two cylindrical bobbins. The ends of the bar which, project beyond the bobbins play between the poles of horseshoe permanent magnets fixed at each. end. The relay is adjusted by moving the stops, and consequently the soft iron bar,to one side or the other. d. 1870. Stroh’s Relay. Two curved permanent steel magnets are fixed side by side on the opposite sides of a vertical bar, whose ends work in pivots. The poles of these magnets play between the poles of two vertical straight electro-magnets. e. 1864. Soft Iron Relay. f. 1855. Varley’s Vertical Relay. The coil is wound on a reel of soft iron, upon each, end of which, a hollow “ casing ” or cap of the same material is fitted, almost completely encasing the coil in soft iron. The armature is crescent-shaped, and is magnetized by induction from a compound bar magnet placed behind. The crescent-shaped poi’tion plays between the inner ends of the casings, which for that purpose do not quite meet, but leave the central portion of the coil exposed. An ordinary magnetic needle pivoted below the coil is acted upon by the latter, and serves as an indicator to call attention. The armature is held up against knife-edge bearings by two helical springs, and the adjustment is effected by varying the tension of one of them. g. 1855. Preece’s Duplex Relay. Worked on the leakage principle. The outgoing current from either station passes through, one coil of the instrument and then divides between the second coil, -which is connected to line and a resistance. h. 1882. Post Office Standard Relay. [25.] 1850. BAIN’S CHEMICAL TELEGRAPH, as used by the Electric Telegraph Company in place of the double needle (No. 7). The paper ribbon was prepared with yellow prussiate of potash, and nitrate of ammonia. The style is of iron. The Steinheil code—dots in two parallel lines—was occasionally used, but was entirely superseded by the Morse code of dots and dashes.