Volume I Part 32 (2/2)

While the arrangement here shown is applicable particularly to the apparatus of the Dean Electric Company, the structure indicated is none-the-less generally instructive, since it represents good practice in this respect. In this drawing the stationary plug shelf with the plug seat is clearly shown and also the hinged key shelf. The hinge of the key shelf is an important feature and is universally found in all switchboards of this general type. The key shelf may be raised and thus expose all of the wiring leading to the keys, as well as the various contacts of the keys themselves, to inspection.

[Ill.u.s.tration: Fig. 299. Magneto Switchboard, Target Signals]

As will be seen, the switchboard cords leading from the plugs extend down to a point near the bottom of the cabinet where they pa.s.s through pulley weights and then up to a stationary cord rack. On this cord rack are provided terminals for the various conductors in the cord, and it is at this point that the cord conductors join the other wires leading to the other portions of the apparatus as required. A good form of cord weight is shown in Fig. 298; and obviously the function of these weights is to keep the cords taut at all times and to prevent their tangling.

[Ill.u.s.tration: Fig. 300. Rear View of Target Signal, Magneto Switchboard]

The drawing, Fig. 297, also gives a good idea of the method of mounting the hand generator that is ordinarily employed with such magneto switchboards. The shaft of the generator is merely continued out to the front of the key shelf where the usual crank is provided, by means of which the operator is able to generate the necessary ringing current. Beside the hand generator at each operator's position, it is quite common in magneto boards, of other than the smallest sizes, to employ some form of ringing generator, either a power-driven generator or a pole changer driven by battery current for furnis.h.i.+ng ringing current without effort on the part of the operator.

[Ill.u.s.tration: Fig. 301. Dean Two-Position Switchboard]

Switchboards as shown in Figs. 294 and 295, are called single-position switchboards because they afford room for a single operator.

Ordinarily for this cla.s.s of work a single operator may handle from one to two hundred lines, although of course this depends on the amount of traffic on the line, and this, in turn, depends on the character of the subscribers served, and also on the average number of stations on a line. Another single-position switchboard is shown in Figs. 299 and 300, being a front and rear view of the simple magneto switchboard of the Western Electric Company, which is provided with the target signals of that company rather than the usual form of drop.

Where a switchboard must accommodate more lines than can be handled by a single operator, the cabinet is made wider so as to afford room for more than one operator to be seated before it. Sometimes this is accomplished by building the cabinet wider, or by putting two such switchboard sections as are shown in Figs. 294 or 299 side by side. A two-position switchboard section is shown in front and rear views in Figs. 301 and 302.

[Ill.u.s.tration: Fig. 302. Rear View of Dean Two-Position Switchboard]

_Sectional Switchboards._ The problem of providing for growth in a switchboard is very much the same as that which confronts one in buying a bookcase for his library. The Western Electric Company has met this problem, for very small rural exchanges, in much the same way that the sectional bookcase manufacturers have provided for the possible increase in bookcase capacity. Like the sectional bookcase, this sectional switchboard may start with the smallest of equipment--a single sectional unit--and may be added to vertically as the requirements increase, the original equipment being usable in its more extended surroundings.

[Ill.u.s.tration: Fig. 303. Sectional Switchboard--Wall Type]

This line of switchboards is ill.u.s.trated in Figs. 303 to 306. The beginning may be made with either a wall type or an upright type of switchboard, the former being mounted on brackets secured to the wall, and the latter on a table. A good idea of the wall type is shown in Fig. 303. Three different kinds of sectional units are involved in this: first, the unit which includes the cords, plugs, clearing-out drops, listening jacks, operator's telephone set and generator; second, the unit containing the line equipment, including a strip of ten magneto line signals and their corresponding jacks; third, the finis.h.i.+ng top, which includes no equipment except the support for the operator's talking apparatus.

[Ill.u.s.tration: Fig. 301. Sectional Switchboard--Wall Type]

The first of the units in Fig. 303 forms the foundation on which the others are built. Two of the line-equipment units are shown; these provide for a total of twenty lines. The top rests on the upper line-equipment unit, and when it becomes necessary to add one or more line-equipment units as the switchboard grows, this top is merely taken off, the other line-equipment units put in place on top of those already existing, and the top replaced. The wall type of sectional switchboard is so arranged that the entire structure may be swung out from the wall, as indicated in Fig. 304, exposing all of the apparatus and wiring for inspection. Each of the sectional units is provided with a separate door, as indicated, so that the rear door equipment is added to automatically as the sections are added. In the embodiment of the sectional switchboard idea shown in these two figures just referred to, no ringing and listening keys are provided, but the operator's telephone and generator terminate in a special plug--the left-hand one shown in Fig. 303--and when the operator desires to converse with the connected subscribers, she does so by inserting the operator's plug into one of the jacks immediately below the clearing-out drop corresponding to the pair of plugs used in making the connection. The arrangement in this case is exactly the same in principle as that described in Fig. 292. The operator's generator is so arranged in connection with this left-hand operator's plug that the turning of the generator crank automatically switches the operator's telephone set off and switches the generator on, just the same as a switch hook may do in a subscriber's series telephone.

[Ill.u.s.tration: Fig. 305. Sectional Switchboard--Table Type]

[Ill.u.s.tration: Fig. 306. Sectional Switchboard--Table Type]

The upright type of sectional switchboard is shown in Figs. 305 and 306, which need no explanation in view of the foregoing, except to say that, in the particular instrument ill.u.s.trated, ringing and listening keys are provided instead of the jack-and-plug arrangement of the wall type. In this case also, the top section carries an arm for supporting a swinging transmitter instead of the hook support for the combined transmitter and receiver.

REVIEW QUESTIONS

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REVIEW QUESTIONS

ON THE SUBJECT OF TELEPHONY

PAGES 11--62

1. When was the telephone invented and by whom?

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