. The practical telephone handbook and guide to the telephonic exchange . in Fig. 55,one pole is furnished with a round coil,b, and the other is attached to a soft-iron cylinder, t, which fits over it, thusforming a box electro-magnet, which concentrates the linesof force due to the operating currents and the magnet inthe centre of the diaphragm. The Collier Receiver.—This is alsoa double-pole receiver in which onlyone coil is used. This coil, withits core, is altogether detached fromthe magnet, the latter being used j\jto polarise the core. The construc-tion is shown in section in Fig.
. The practical telephone handbook and guide to the telephonic exchange . in Fig. 55,one pole is furnished with a round coil,b, and the other is attached to a soft-iron cylinder, t, which fits over it, thusforming a box electro-magnet, which concentrates the linesof force due to the operating currents and the magnet inthe centre of the diaphragm. The Collier Receiver.—This is alsoa double-pole receiver in which onlyone coil is used. This coil, withits core, is altogether detached fromthe magnet, the latter being used j\jto polarise the core. The construc-tion is shown in section in Fig. coil is fixed in a central blockof ebonite, and side cheeks ofebonite screwed on to this blockserve to clamp two soft-iron dia-phragms very close to the twoends of the core. On the outsideof these cheeks the two magnetpoles are fixed in contact with twosoft-iron adjusting screws broughtvery near the outer faces of thediaphragms. The top of the in-strument is shaped for fitting tothe ear, and is put into communi-cation with the internal spaces between the diaphragms. icale | RECEIVERS IN GENERAL USE 69 and the sides of the bobbin by small holes, as shown. Theends of the coils are connected to terminals, a and b. The diaphragm and coil being in a strong magnetic field,the core of the coil is strongly magnetised by induction. Theinstrument is efficient, but is too bulky for ordinary is, however, often used as a loud-speaking instrument. The Watch Receiver.—This is a double-pole receiver of aneat, light, and compact form, a little larger than an ordinarywatch. Fig. 57 gives an interiorview of one form. Hand-Micro-Telephone.—The re-ceivers used in connection withthe hand-micro-telephone type ofinstrument, now so commonly em-ployed in this country, are of asimilar type to Fig. 51, the magnetsbeing either of the ring pattern, asshown in Fig. 52, or similar tothose of Fig. 57. Relation between Strength of Mag-net and Size of Diaphragm.— conducted a series of
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelephone, bookyear19
