Switchboard

“ The switch arm, to which the handle is attached below, does not itself make and break the circuit, but carries a spring, as shown, which, when the arm is at the end of its movement, pulls over the contact lever with a rapid action, shooting the same between the divided contact piece, and making a perfect contact. The switchboard forms one side of a closed wooden case or cupboard, with sufficient room for a man to enter and adjust the resistances or switches for each lamp. ”

“ For the serving of a large traffic from a large number of lines, as is required in practically every city of the world, a very great contribution to the practical art was made by the development of the multiple switchboard. Such a switchboard is merely such a device as has been described for the simpler cases, with the further refinement that within reach of each operator in the central office appears every line which enters that office, and this without regard to what point in the switchboard the lines may terminate for the answering of calls. ”

“ When the traffic originating in a switchboard becomes so great as to require so many operators that the board must be made so long that any one of the operators cannot reach over its entire face, the simple switchboard does not suffice. Either some form of transfer switchboard or of multiple switchboard must be used. ”

“ If you could only forget that there are thousands of circuits here, you would understand it very readily. It is the repetitions that make it seem so complicated, Now, this switchboard is divided into two parts. We call one the ‘A’ board, it takes up about two thirds of the room; and the other is the ‘B’ board. Suppose you were a subscriber connected with this central, and wished to call up some one also connected with this central. ”

“ The ideal (switchboard) system would be one in which the operator would receive the orders to connect and disconnect from the subscriber orally, by means of a head telephone; to have in front of her a switchboard by which she could connect any two wires of the whole system, however large, without interfering with the other operators. ”

“ High wiring is carried entirely on the roof of the car where it is entirely out of the way and where the operator cannot come in contact with it. The switchboard should be of the utmost simplicity. Usually the negative and equalizer switches, and the field break-up switch are mounted on the frame of the converter. The double throw switch for starting and running the converter can be mounted under the floor of the car and operated by handle at the switchboard. The rheostat can be mounted back of the switchboard on brackets bolted to the car super-structure. ”

“ Switchboard drops in falling make but little noise, and during the day time, while the operator is supposed to be needed continually at the board, the visual signal which they display is sufficient to attract her attention. ”

“ Behind this all the wires converging in the office concentrate. The board accommodates 400 different lines. In October, 1878, the parent 'Bell Telephone Company' issued a circular describing a form of brass strip switchboard 'adapted for six circuits.' On February 20, 1879, a circular was issued describing a switchboard which could be supplied at
from 50 cents to $1 per circuit, according to the number of circuits. ”

“ The electrically operated switches may be of the open type, mounted on a slate or marble switchboard, when the whole control outfit is placed in a room which is comparatively free from dust or dirt of any kind, and where there is no danger of employees coming in contact with the switches. The other type of switch is entirely enclosed, the main contacts being oil immersed. ”

“ This makes it apparent that if there is any economy in this type of multiple switchboard, it must be found in the very small boards where there are but few jacks per line and where the extra cost of the cut-off jack is not enough to offset the extra cost of an added relay. It is the growing belief, however, among engineers, that the multiple switchboard must be very small indeed in order that the added complexity of the cut-off jacks and wiring may be able to save anything over the two-relay type of line ”

“ In those towns equipped with magneto systems employing simple switchboards or transfer switchboards, and which require new switchboards by virtue of having outgrown or worn out their old ones, the magneto multiple switchboard is frequently found to best fit the requirements of economy and good practice. ”

“ Carstairs strode up on to the switchboard, very alert, but very cool. He switched out all the switches, replaced the fuses by bigger ones, and switched in again, the switchboard attendant assisting him in a high state of nervous excitement. Now there is a piece of apparatus known as a magnetic automatic circuit breaker. It is carefully designed to come out at the wrong time and stay in at all other times; the good chief of Southville, in the simplicity of his trust in catalogues, had, "for safety," as he expressed it, two of these devices fixed on every machine ”

“ You could put the entire equipment in a dray. Our switchboard is about as big as an old-fashioned china closet and has three hundred drops. I suppose an up-to-date telephone manager has forgotten what "drops" are and you can't be expected to know. But out our way the telephone companies are coöperative, and as every subscriber owns a share, we all take a deep personal interest in the construction and operation of the plant, discussing the need of a new switchboard and the advantage of cabling the Main Street lead, in technical terms. ”

“ It furnishes many similes of graphic helpfulness in understanding more nearly much truth of the Spirit life.
In the power-house where the electricity is being wooed into man's harnessing, or generated, as the experts say, is found a switchboard, or switch-room with a number of boards. Here in a large city plant a man may go and turn a switch, that is, move a little handle, a very short distance. ”

“ Thus, when the cord circuit of a metallic-circuit switchboard is used to connect two grounded circuits together, the tip strand of the cord is the connecting link between the two conductors, while the sleeve strand of the cord merely Page 362 serves to ground one side of the clearing-out drop and one side each of the operator's telephone set and the ringing generator when their respective keys are operated. ”

“ In that way I learned a great deal about the arrangement and construction of switchboards. Encountering the trouble first, I had an advantage over others in being able to suggest a remedy. So I have always thought it was a good thing to have troubles, as long as they are not too serious or too numerous. Troubles are certainly a great advantage, if we manage them correctly.
Certainly Carty made these switchboard troubles the first stepping-stone in his climb to the top in the field of telephone engineering. ”

“ Probably the most important piece of apparatus in the multiple switchboard is the jack, its importance being increased by the fact that such very large numbers of them are sometimes necessary. Switchboards having hundreds of thousands of jacks are not uncommon. The multiple jacks are nearly always mounted in strips of twenty and the answering jacks usually in strips of ten, the length of the jack strip being the same in each case in the same board and, therefore, giving twice as wide a spacing in the answering as in the multiple jacks. ”

“ By a specially complicated arrangement of the already complicated switchboard, it was possible to run any machine on any feeder. The Shift Engineer signalled for another machine, and Carstairs plugged her in on the faulty circuit. The fuse held for about one minute, then it blew with a flash and a bang right in Carstairs' face. ”

“ Machine-Switching System.—A retrospective examination of the manually operated switchboard discloses the fact that the tendency of development has been continuously in the direction of increasing the number and extent of the operating functions which are performed electro-mechanically and likewise decreasing the amount of time required of the operator for the handling of the connexion. ”

“ The ground on the conduit system is not to be considered as a ground for a secondary system.
Guards. Guards.—A guard rail should be provided around the stage switchboard to prevent actors from coming in contact with any live part of the switchboard. All incandescent lamps about the stage, dressing rooms, fly-floor, grid-floor, etc., should be provided with guards.
Hanger-Boards. Hanger-Boards.—Hanger-boards are not compulsory [267] but where not used, arc lamps must be hung from insulating supports other than their conductors. ”

“ The simplest form of switchboard is that for serving small communities in rural districts. Ordinarily the telephone industry in such a community begins by a group of farmers along a certain road building a line connecting the houses of several of them and installing their own instruments. This line is liable to be extended to some store at the village or settlement, Page 374 thus affording communication between these farmers and the center of their community. ”

“ The line connects the levers together perpendicularly. The springs being connected horizontally, form the connecting bars. Any two circuits are connected by throwing the corresponding levers on the same row of springs. We have testimonials from parties using the switch, where one operator does all the work satisfactorily for three hundred subscribers, where with any other system it would require at least two, thus making a permanent saving in the running expenses. A cheaper type of Snell switchboard is shown in Fig. ”

“ The operator’s telephone is usually equipped with a hand set, (receiver and transmitter) which leaves him with only one free hand for making connections.
4. One switchboard is equipped with but one master, or operators cord, this affords only one means of answering and calling.
Advantages of the Monocord Switchboard.
1. Small, compact, light weight.
2. Simple wiring.
3. Quickly installed.
4. Particularly suited for small central exchanges.
5. Units can be removed quickly, in case of trouble in interior circuits. Any unit can be removed without disturbing other units. ”

“ Soon, therefore, it became obvious that the telephone switch must be compact; all the apparatus must be easily and quickly under control; everything about it must be well made and well put together; the motions required in a connection must be reduced to a minimum, and yet the apparatus must be cheap. The cry of cheapness for a long time obscured the vision of the practical man. In 1881 came the first of the multiple switchboards. This innovation was arranged for grounded and later for metallic circuits, and was designed to eliminate many of the causes tending to slow down the service. ”

“ The switchboards in large cities are necessarily very complicated affairs, and it requires a number of operators to answer the many calls that are constantly coming in. Each central-station operator presides over a certain section of the board, and as this section has to be related in a certain way to every other section, it is easy to see wherein arises the complication. ”

“ Not far away a switch-engine stood, leisurely working the pump of its air-brake, emitting steamy sighs, as if it were snatching a moment's rest from its labors. On the damp and heavy air the voices of the engineer and fireman were borne to them. At times other switch-engines slid up and down the tracks. Curly and Archie sat down in the shadow of the lumber and waited. After a while, down the rails a white light swung in an arc, the resting switch-engine moved and began to make up a freight-train. ”

“ The switch is operated by the rise and fall of a copper float which is connected to the switch lever by a brass rod or copper chain. As the water level rises and falls, the float moves up and down. This movement is transmitted to the switch lever and the switch (if the movement be sufficient) is tripped to make or break the motor circuit. To insure the best operation it is necessary that the float rod be provided with a guide so that the float will move up or down in a vertical line, as shown. ”

“ The other illustrations show how the same method of construction may be applied to make switches having more than one "point" or contact.
No dimensions have been given for constructing these switches, because it is doubtless easier for the young experimenter to use materials which he may have at hand, and construct a switch of his own proportions. Only one suggestion is necessary, and that is to bevel the under edges of the arm with a file, so that it will slip over the head of the brass tack more easily. ”

“ A switch is a piece of apparatus for making, breaking, or changing the connections in an electric circuit.
The particular form and construction of any switch is governed by the electrical conditions under which it must operate.
Since the electric current cannot be stopped instantly when the circuit in which it is flowing, is broken, an arc is formed as the switch contacts separate; this tends to burn the contacts, and to short circuit, the severity of such action depending on the voltage and the proximity of the switch terminals. ”

“ FIG. 18. HOW THE DECK IS MADE.
Cut out a rectangular hole 1⁄2 inch wide and 2 inches long in the for’ard end of the deck, for the screws and the wires of the switch to pass through. Screw the porcelain block of the switch to a board of the same size, with the tin deck in between them; this insulates the screws of the switch from the tin, which would otherwise short circuit the battery and run it down. Run sealing-wax in and around the edges of both the porcelain and wood blocks to make a watertight joint, for water must not get into the boat. ”