Improvements in Telephone Selecting Systems

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