Patent GB-190413216-A (GB)
Title: Improvements in Telephone Exchange Systems.
Inventor: AITKEN WILLIAM
Filed: 1904-06-11
Granted: 1904-09-29
Abstract: 13,216. Aitken, W. June 11. Telephone systems.- Relates to centralbattery systems, in the cord circuits of which condensers are used instead of repeater coils; also to a transfer system, and to a special form of relay. Fig. 3 shows a type of cord circuit for use with the ordinary multiple jack lino circuit illustrated in Fig. 1. When the plug A is inserted in the jack h, the receiver being off the hook, a circuit is completed from the battery k through the retardation coil d, the line circuit, and the relay e to earth. Another circuit is also completed from the battery k through the relays e<2>, e' to earth. Both relays e, e<2> being energized, the lamp does not glow. When the plug B is inserted in the required jack, the condenser corresponding to c<2> prevents current from flowing through the relay e', and the lamp j<1> lights up till the receiver is removed. In a modified form of cord circuit, the relays e<2>, e<3> are replaced by resistances, and the lamps are placed in series across the sleeves a', b<2> and are shunted by the armatures of the relays e, e<1> when the latter are energized. In the line and cord circuits of another system, shown in Figs. 5 and 7 respectively, the relay e and retardation coil d are placed in the line instead of the cord circuit. The local circuit of the relay e includes the lamp j<2> and the telephone meter or resistance x. For calling, a circuit is completed from the battery k through the line and relay e to earth, and the lamp j<2> glows. When the plug A is inserted, the linewires are connected to the operator's telephone y, and a local circuit is completed from bush 3 through the meter key x<1> and relay e' to earth, the lamp j<2> and the supervisory lamp j being thereby shunted. The line required is tested, and, if it be engaged, a current passes from the bush 3 by the tip b and speaking-key springs through one half of the telephone y to earth. If, however, one of the engaged subscribers has hung up his telephone, there will be no current on the bush 3, but the induced current from a transformer w, having a commutator in its primary circuit, will give the click. When the plug B is fully inserted and the key f is moved to the through position, the relay e<2> is not energized and the lamp j<1> glows, till the receiver is taken off in answer to the operator's ring-up. At this stage, the call is recorded by the operator depressing the meter key x<1>, causing the battery k<1> to supplement the battery k and the shunt e' to be removed. The line circuit for a non-multiple switch-board system, is shown in Fig. 8, the plugs being two-way only and having condensers in circuit. A service plug may be but used for introducing the operator's telephone, the usual speaking and ringing keys are preferably used. When calling, the circuit through the lamp j is completed by the relay e through the springs 3, 4 to earth. When the plug A is inserted, the spring 4 is separated from the spring 3 and connected to the other 5, so that, when the receiver is replaced and the relay e de-energized, the lamp j lights up again as a clearing-signal. In a modified form of this system, separate clearing signal lamps are connected in series across the outer sleeves of three-way plugs. The bell in the instrument circuit is connected directly to earth. The back contact of the relay e is connected to earth and the armature is connected to the bush 3. The lampj is connected to earth and to the bush 3 by a spring contact which is broken on the insertion of the plug. The line and cord circuits of a multiple switch-board ring-through system are shown in Figs. 12 and 13. When the plug A is inserted, a circuit is completed from the battery k through resistance i and relay e<2> to earth, and the lamp j goes out. Another circuit is completed from the battery k, Fig. 13, through one winding of the differential relay e and the coil d over the line, and back through the other coil d and the second winding of the relay e to earth. When the plug B is inserted, the receiver being on the hook, the line 1 is connected through the bell to earth, while the line 2 is insulated, the relay e' is energized, and the lamp j<2> glows. The operator gives an initial ring-up by means of the key g, but the calling subscriber can also ring, while keeping his receiver off the hook, the receiver being shortcircuited by the springs r<1>. When both instruments are replaced, lamps j<1>, j<2> light up, the circuit being from the battery k through one winding of relay e and the coil d to the switch-hook and bell to earth. The junction circuit of a transfer or manual-distribution system is shown in Fig. 14, the line circuits being similar to Fig. 1. The calling and answering jacks are on the calling and distributing boards, the " A " boards, while the multiple jacks are on a separate board, the " B " board. Each A operator has connection with a number of B operators, and, when making connections, the B operator gives a " busy signal to the A operators. Of the signal lamps j<4> to j<9>, one is situated in front of the B operator and the others in front of the A operators. The battery is connected to the lamps when the operator is on duty, by means of the connector W. When the plug A is inserted, the battery k is connected through relay e<2>, lampj, and relay e<4>, Fig. 1, to earth. A circuit is thereby completed from the battery k through the contacts of relay e<3>, lamp j<2>, and the contacts of relay e<2> and relay e, the latter being energized by the current in the line circuit. The lamp j<2> on the B board glows, and the operator moves the key f, giving the busy signal and bring- ing her telephone into circuit. The B plug, being inserted, completes a circuit from the battery k through relay e<3>, lamp j<1>, and the cut-off relay to earth. The circuit of the lamp j<2> is thus broken. The clearing-signals are received as described with reference to Fig. 3, both clearing-lamps being on the B board. The withdrawal of the plug B deenergizes the relay e<3> and completes a circuit from the battery k through the contacts of relay e<3>, lamp j<2>, contacts of relay e<2> and relay e, and the lamp j<3> to earth. The lamp j<3> being the clearing-signal to the A operator, the plug A is then withdrawn. Any form of relay may be used, but that shown in Fig. 15 is preferred. The core 1 carries a shaped pole-piece 2, and an angle-iron piece 3, the front of which is finished flush with the cheek 4. The armature 8 is carried by but insulated from the spring 5, which may also form a connecting-spring. The armature and pole-piece have their meeting faces half-cut or rabbeted as shown.