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exchanges resulted. These exchanges is already in operation; and others will be were successful, not so much in what added as occasion demands, the ultimate they actually accomplished in the way purpose being to handle the business of of improved service, as in the promise the entire city. they gave of future development in that

The Automatic Mechanism direction. The apparatus was crude, imperfect, and complex; but the funda A study of the apparatus which has mental ideas involved were right and made all this possible will, no doubt, be required only better expression.

interesting and instructive. The tele

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Ten years passed, ten years of experi- phone itself resembles, in many particument and persistent effort. Strowger lars, the manually operated telephones died. The Automatic Electric Company with which we are so familiar. It conwas organized to take over the Strowger. sists of the usual transmitter, receiver, patents. Further experimenting was » bells, battery, and induction coil, adding done, and greater capital expended. The only a calling dial, a circular metal piece, result has been a system from which the on the periphery of which are ten finger imperfections have been eliminated, a holes numbered 1-2-3-4-5-6-7-8-9-0. A system which is scarcely more complex stop is provided at the lower of the holes than the manual switchboards now in to limit the distance which the dial inay general use. The limit of capacity is no be made to revolve. longer reached at 1,000 stations. In fact, the business of the very largest city can

How a Call is Made be handled as efficiently and conveniently The method of calling is very simple. as that of a town which requires but a To secure a number, say 761, the subhundred telephones. In Chicago to-day scriber first takes the receiver from the an automatic exchange of 10,000 stations hook; then, placing his finger in hole

number 7, pulls the dial around to the stop above mentioned. When released, the dial is instantaneously restored to its normal position. The subscriber is now connected to a trunk line leading to the seventh group of so-called "connector”.

dial, but on the return. This is arranged for the protection of the instrument against careless or hasty subscribers. The return of the dial is regulated by a governor which always insures proper speed:

The calling mechanism may be said to be perfect. It is simple, and works with remarkable accuracy, speed, and precision.

The Switch The switch, shown in the accompanying illustration, is a device about 13 inches in height, 472 inches in depth, and 4 inches in breadth. The upper half of this device consists of two relays and

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Wall TELEPHONE. 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 1 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

AUTOMATIC TELEPHONE Switch.

Front View.

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.

Accessories The accessorial equipment consists of a 52-volt storage battery, which furnishes the current for operating the switches ; a cross-connecting board or distributing rack, equipped with carbon lightning arresters and heat protectors; a ringing machine with “busy back” and “howler"

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AUTOMATIC TELEPHONE Switch.

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

INTERIOR OF Wall TELEPHONE, is one for every telephone connected with the exchange, and the other as “connect- attachment; charging machines; power ors,” of which there are ten for every board, on which are mounted the usual hundred selectors and which are in knife switches, circuit-breakers, voltgroups each capable of connecting one meters, ammeters, etc., necessary for

cation-an advantage that cannot be overestimated by the general business man, as well as by the broker, the lawyer, and the physician.

6. The subscriber himself instantaneously connects with the person he wishes to call; and the apparatus is so constructed that it is an impossibility for another subscriber to "cut in” or in any way interfere with the line he is

7. The frequent delays and mistakes which the manual board causes are entirely unknown to users of automatic telephones. The switches

controlling and measuring the current; and a “tell-tale" board.

This last consists of a number of 8candle-power lamps mounted on a marble panel, together with a magneto bell. In case of a short circuit or “ground” on any line, the bell rings and the lamp on the panel glows. The position of this lamp instantly indicates to the attendant the exact location of the trouble, and ofttimes enables him to rectify it before the subscriber is aware that there has been any trouble.

The automatic switches are mounted on steel shelves, twenty-five to the shelf, each board containing four shelves of first selectors, and one shelf of connector switches. This is the arrangement for a system of 1,000 stations. In a 10,000-station system, the board is made up of six shelves, four of first selectors, one of second selectors, and one of connector switches. The floor space occupied by such a switchboard is II feet 6 inches by 12 inches. The switchboard is made of steel angles and is rigidly braced.

A very important feature of the automatic switchboard is that it can be increased to any capacity by simply adding new sections with the desired number of switches mounted thereon, without in any way interfering with existing conditions. Ninety-five per cent of the electric contacts and connections are made at the factory; consequently better results are secured, as well as time and expense saved in installation.

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Advantages of the Automatic System

I. A switchboard has no operators; and thus one of the large fixed charges incident to manual-exchange operation is eliminated.

2. There being no operators, the automatic exchange can be located in less expensive quarters than the manual. No reading or retiring rooms are needed, no lockers, no lavatories; and the cost of fuel and lighting is reduced.

3. One switchboard attendant, for testing and keeping apparatus in order for 1,000 subscribers, is all that is needed in the automatic practice.

4. The cost of maintenance and interior equipment is no greater, and in large exchanges is less than in the manual exchange.

5. The service which the automatic system gives, unlike that of the manual system, is absolutely secret, each subscriber having a "private wire" on which to transmit his communi

AUTOMATIC TELEPHONE Switch.

Rear View. do not make errors nor gossip; are never weary or sleepy; are not interested in subscribers' affairs; and are not impudent.

8. The complexity of the automatic exchange does not increase proportionately to the increase of size, as is the case with manual exchanges, where the cost of giving service is much more per subscriber in large than in small exchanges. The cost of operation in the automatic exchange is fixed. An increase is merely a matter of adding new telephones and switches, the cost of operation being the same per subscriber.

9. The automatic switch is thoroughly cosmopolitan in its nature, no interpreter being needed by the foreigner in a country where the automatic exchange is located, any person being able to secure the desired connection by simple rotations of the dial.

10. The same number of automatic switches are always at work, night and day.

II. Quick connections, instantaneous accommodations, prompt answers, accuracy, and promptness, with the busy signal given when subscriber called is busy.

Life Under Water

A Night's Experience on a Holland Submarine

Before retiring for the night, the crew had an excellent supper. The cooking, as well as the lighting, was done by electricity. The air reservoirs were filled to their full capacity of 40 cubic and when the Fulton rose to the surface in the morning, after being under water for twelve hours and twenty-three minutes, there was hardly a perceptible dif

INCE the new Holland submarine torpedo-boat, the Fulton, spent a comfortable night on the bottom

of Narragansett Bay, the public have felt that Jules Verne and his fabled Nautilus are a good deal of a reality.

On the evening following the speed and fire tests, the Board of Inspection appointed by the Navy Department decided to test the Fulton as to the comfort of the men who had to live in her. It was therefore decided that the boat should spend the night at the bottom of the bay.

This was the first test ever made under naval supervision, to determine whether men can live aboard a submarine boat under water as safely as on the surface.

All the necessary preparations were made, and at seventeen minutes to eleven, the Fulton sank with nine men aboard.

One of the features of the crew's experience was the distinctness with which sound was conveyed under water. Early in the morning the submerged crew were awakened by what was afterwards explained to be the Fall River steamer touching at Newport on its way from New York. Although the steamer did not pass within a mile of the submerged Fulton, several of the crew of the submarine were awakened by her plowing through the water.

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