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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

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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 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

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 "busv back" and "howler"

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Interior Of Wall Telephone,

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

Advantages of the Automatic System

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1. 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

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 using.

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

Automatic Telephone Switch.
Rear View.

do not make errors nor gossip; are never
weary or sleepy; are not interested in sub-
scribers' 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.

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SINCE 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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THERE ARE TIMES when electricians are called upon to locate faults in bell and gas-light circuits, and will spend much time in trying to find the trouble. Everything will appear to be in good condition; but the batteries do not last long and finally give out entirely.

The reason for this nuisance, nine times out of ten, is found in a small leakage of current, which may be detected by means of a sensitive telephone receiver. Of course the leak cannot be located by the receiver; but if the electrician knows that there is a leak, he can find out where it is, being careful to examine fixtures, piping, damp places, etc., where the wires are run.

Electric Gas-Lighting Circuits

Referring to the sketch of the first test (Eig. 1), the receiver is connected to the points A and B; then the connection is made as indicated in the sketch of the second test (Fig. 2) ; and a comparison of the two sounds, made in the receiver at the time of connection, is taken. This comparison will give an idea as to the amount of leakage, if any exists. If there

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