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Its Mechanism Popularly Described—Its Advantages over Manual Operation



HE SPIRIT of the present age is not better shown forth than by the ever-increasing demand which industry, pressed by the keenness of competition, is making upon genius for the invention of labor-saving and time-saving machinery; and nothing pays higher tribute to the breadth of the human intellect than the character of the machinery which has been evolved as the result of this insistent call. Indeed, we are sliding rapidly into an automatic age. The work that once was done by hand, then by hand-guided machines, is now done by automatic devices. Scarcely a large, up-to-date factory but has in one or more of its departments a battery of automatic machines busily engaged in turning out such things as screws, buttons, tin cans, cloth, shoes, or a thousand other varieties of useful articles from the raw material, with surprising nicety and tremendous speed, reducing the cost of manufacture to a minimum and widening the field of sale. We have wondered at the ingenuity of these machines and marveled at their cleverness,

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Few of us, however, as we have stood before a telephone box, wiggling a switch hook, or whirling the crank of the hand generator, and impatiently waiting for time and the "Hello girl" to bring us our connections, have ever gone so far as to hope, or even conceive the idea, that this genius who had so long presided over the central office, would ever be unseated and her place occupied by an iron machine whose speed and accuracy would discount her best performances; and yet that day is here. The States are already dotted with automatic telephone exchanges, which are giving service to thousands and thou

sands of subscribers, and with such success that it is not hazarding anything to predict that a few years will see the absolute divorce of the operator from the exchange room-except, of course, for long-distance calls, for which her services will probably always be needed.

Historical Retrospect

The application of the automatic idea. to telephony is not new. It is considerably more than a decade since Strowger, an obscure Chicago engineer, brought out the first automatic telephone. The Strowger Automatic Telephone Company and the installation of a number of small

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Ten years passed, ten years of experiment and persistent effort. Strowger died. The Automatic Electric Company was organized to take over the Strowger patents. Further experimenting was done, and greater capital expended. The result has been a system from which the imperfections have been eliminated, a system which is scarcely more complex than the manual switchboards now in general use. The limit of capacity is no longer reached at 1,000 stations. In fact, the business of the very largest city can be handled as efficiently and conveniently as that of a town which requires but a hundred telephones. In Chicago to-day an automatic exchange of 10,000 stations

phone itself resembles, in many particulars, the manually operated telephones with which we are so familiar. It consists of the usual transmitter, receiver, bells, battery, and induction coil, adding only a calling dial, a circular metal piece, on the periphery of which are ten finger holes numbered 1-2-3-4-5-6-7-8-9-0. A stop is provided at the lower of the holes to limit the distance which the dial may be made to revolve.

How a Call is Made

The method of calling is very simple. To secure a number, say 761, the subscriber first takes the receiver from the hook; then, placing his finger in hole

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Showing Method of Operating Dial and Making Call.

switches, which we may call the "seven hundredth" group. In the same manner he calls 6 and I in this group. Having turned the number desired, he presses a button underneath the dial, which rings the bell of the person wanted, and the connection is completed. In the event that the 'phone of the subscriber called is busy at the time of the call, a vibratory sound in the receiver of the caller notifies him that such is the case.

The keyboard or internal mechanism of the telephone, occupies a space 5x3x2 inches, and consists of an impulse-sending mechanism, which, in response to the rotations of the dial, communicates to the subscriber's switch a number of impulses corresponding to the number of the hole in which the finger is placed, lifting the shaft which occupies the central position of the switch, up to the proper row of contacts, and bringing the "wiping fingers" fastened thereto into connection with the proper contact in that row.

It should be understood that, when the call is made, no impulses are sent over the line on the down movement of the


three pairs of magnets mounted on a solid cast metal base. These relays and magnets, together with the proper springs, wires, etc., operate a vertical rod

in the center, in obedience to the impulses sent from the subscriber's telephone, and bring the three pairs of "wiping fingers" attached thereto into connection with the

hundred telephones. The function of the selector is to connect the calling telephone with the connector in the proper group, which in turn connects with the telephone desired in that group. This is the case in exchanges of one thousand capacity or less. In larger exchanges a second collector is employed. This is an intermediate switch, and divides the work of selection with the first selector.

Trunk-Selecting System

The trunking system employed is very much akin to that now generally used in manual practice and, therefore, needs no description here. It may be said, however, that the selection of trunks is automatically accomplished, the "wiping fingers" on the shaft of the selector switch passing over all busy contacts and stopping at the first idle point.

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Side View.

brass contacts, which, arranged in three semicircular banks, constitute the lower half of the switch.

The upper of these banks, known as the "busy bank" serves to indicate busy lines in the automatic selection of trunks. The lower two are "line banks," to which the line wires connect, and over which the conversation is held.

Two classes of switches are employed, one known as "selectors," of which there is one for every telephone connected with the exchange, and the other as "connectors," of which there are ten for every hundred selectors and which are in groups each capable of connecting one.


attachment; charging machines; power board, on which are mounted the usual knife switches, circuit-breakers, voltmeters, ammeters, etc., necessary for

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