Patent GB-190411274-A (GB)
Title: Improvements in Telephone Selecting Systems.
Inventor: WATKINS WILLIAM DAVID
Filed: 1904-05-16
Granted: 1905-01-12
Abstract: 11,274. Watkins, W. D. May 16. Telephone systems ; ; telephone calls.-In a party line system, two continuous line wires 1, 2, Fig. 1, are used, and the subscribers' instruments may be connected between these and the earth ; but, normally, each subscribers' bell 80 and receiver are disconnected at 28, 96, respectively, and can be connected only by a selecting-apparatus operated from the exchange. The exchange is called automatically when a subscriber lifts his receiver from its hook lever, the lever being raised by a spring and having guides carrying a rolling weight with a pin in engagement with a slotted switch lever 116 ; the weight moves along the guides and carries the switch 116 over a definite number of stationary contacts 111, and the line wires 1, 2 are thus connected together, through springs 94, 95, a number of times peculiar to each subscriber. At the exchange, the line wires 1, 2 are permanently connected together through a battery 4 and the electromagnet of a step-by-step indicator 3, which thus shows the number of the calling subscriber. The switch 116 remains on a contact, so that the circuit of the central battery is closed through the indicator, and no other call can be received until the first has been attended to. The exchange calls a subscriber by closing a switch 9 a definite number of times, between the central battery 4 and earth, to excite a selecting-electromagnet 12, which is permanently connected between the second line wire and the earth, in each subscriber's apparatus. The electromagnet 12, Fig. 6, oscillates a pivoted armature 14 in opposition to a spring, and the armature carries pawls 65 to rotate two ratchetwheels 40, 41 in opposition to springs. The selector, Fig. 6, is in a separate case, in order that the noise made by its operation may not annoy the subscriber. When the disc 41 begins to turn, a pin on it leaves a spring-pressed detent 51, which then prevents reverse movement of the disc 40. A loose arm 49 is provided with a pin to engage in any of a number of holes in the disc 40, and thus forms a projecting stop determining the starting- position of the disc 40 in each selector. The armature 14 is caused to oscillate until, at the station to be called, a notch 45 in the disc 40 is under the end of a pivoted arm 22 ; the exchange switch is then held closed for a time, allowing the disc 41 to return to its starting-position, so that a second pin on the disc 41 turns a bell crank 35, and this withdraws a pivoted catch 30 from under the arm 22, which then falls into the notch 45. The arm 22 depresses a rod 24 and spring 26 to make contact at 28. The first-mentioned pin on the disc 41 then also withdraws the Jeteat 51 from the disc 40. When the switch at the exchange is opened, an arm 33 of the armature 14, raises the arm 22, which allows the disc 40 to return to its starting- position, and the spring 26 to rise. While the bpring 2G is depressed, part of the current from the exchange, passes through it and the electromagnet 80, Fig. 1, of the subscriber's call-bell, to earth. The electromagnet 80 then attracts a wire lever, and this passes a projection on a spring 96, by which the wire lever is retained. The spring 96 separates the spring 94 from the spring 95, thus opening the circuit of the subscriber's calling- switch 116, 111. The contact of the springs 96, 94 connects the subscriber's receiver and inductioncoil secondary between the line wires 1, 2, through the hook lever. The hook lever closes the local circuit of the subscriber's battery, transmitter, and coil primary. When a subscriber places his receiver on the hook lever a sliding spring is depressed and causes the wire lever to move away from the ball electromagnet 80 ; the spring 96 thus immediately opens the circuit of the receiver.