Fig. 304. Sectional Switchboard—Wall Type
[View full size illustration.]

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.

Fig. 305. Sectional Switchboard—Table Type
[View full size illustration.]

Fig. 306. Sectional Switchboard—Table Type
[View full size illustration.]