made for plugging each generator feeder on to any one of the four pairs of 'bus bars provided. Fig. 164 is a front view of the generator switchgear. The battery regulating switches can just be seen at the top of this

FIG. 163.-Section through Hackney L. T. switchgear.

photograph, supported from the ceiling over the switchboard gallery. These switches are controlled by handles fixed at the lower extremities of vertical shafts supported in the centre of the switchboard. Bevelled wheels at the top of these shafts engage with horizontal shafts upon which

the worm wheels driving the screw shaft of the regulating switches are fixed.

The positive and negative generator panels are fixed respectively to the

right and left of the battery controlling gear. In addition to the field switches on the front of the panelled desk, at the bottom of the switchboard two cases are fixed, each containing twenty fuses, in which the feeder pilot wires terminate. A twenty-way pilot wire voltmeter switch is fixed above

each set of fuses.

Fig. 165 is a reproduction of a photograph taken from one end of the switchgear, showing the generator gear on the left, and the feeder gear on the right of the illustration.

FIG. 165.-End view of Hackney board, showing back-to-back arrangement of

Boston, U.S.A., Switchgear.

An interesting example of American practice in the arrangement of low-tension switchgear is to be seen at the Atlantic Avenue station, Boston.

The generating plant at this station is divided into two distinct enginerooms, and the switches and other controlling apparatus are arranged in a separate room. This switchboard room is entirely shut off from the engine-rooms, but the switchboard attendant can signal to the attendants in either engine-room by means of dial posts of the Cory system of engine telegraphs. Each signalling set consists of one disc signifying the engine or booster in question, and a second disc denoting the instructions to be given regarding that unit. A sectional view of the switch-room is

shown in fig. 166. All the recording and indicating instruments are fixed. on a gallery running all round the switch-room, the apparatus controlling the generators being on the section of the gallery at one end of the room, with the feeder panels on each of the side galleries. The actual generator switches are placed on the ground floor, and are motor controlled by relay switches on an operating desk situated near the generator section of the gallery. The operating desk and instruments for the generator section are not shown in fig. 166, but the approximate position of this apparatus is indicated by the letter A.

There are at present forty motor-driven main generator switches. These are arranged in two rows parallel with the side galleries, there being twenty positive switches in one row, and twenty negative switches

in the other row.

Room is left for two more rows of switches in the positions where they are shown dotted. These switches are used to connect the positive and negative leads from the generator on to either