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are used where wires are to be led into a building or to supply a street branch. Fig. 18 shows the method of running several tubes into a man-hole and connecting all together there.
To return to the station, Fig. 19 shows the general arrangement of the electric devices therein. Here are shown three units or couples of dynamos; each individual dynamo having a regulator for controlling the amount of current passing through its magnet coils.
The three heavy lines running nearly the full length of the figure are what are termed the "Bus" wires, and are marked respectively, positive, negative and neutral, as shown by the signs attached to each.
The object of these wires is to receive the total current delivered by the units, and conduct the same to the feeders for distribution to the outside mains. It will be observed that one wire from each of the couples of dynamos passes to the neutral bus, while the other two wires pass to the positive and negative buses, re-
