[Electric engineering.] . by means of couplingboxes, or junction boxes. These are placed on the sidewalls of the manholes and are made water-tight. Fig. 22shows a coupling box. A, B, and C are the three maincables, or feeders, of a three-wire system that are to be 15 ELECTRIC TRANSMISSION. 19 coupled to the three cables A, B, C. The cables enter thecast-iron box through rubber gaskets that are clamped so asto make the box water-tight. Each cable is provided witha terminal on the end, and these terminals are connectedtogether by pieces of copper bar securely clamped againstthe terminals by the
[Electric engineering.] . by means of couplingboxes, or junction boxes. These are placed on the sidewalls of the manholes and are made water-tight. Fig. 22shows a coupling box. A, B, and C are the three maincables, or feeders, of a three-wire system that are to be 15 ELECTRIC TRANSMISSION. 19 coupled to the three cables A, B, C. The cables enter thecast-iron box through rubber gaskets that are clamped so asto make the box water-tight. Each cable is provided witha terminal on the end, and these terminals are connectedtogether by pieces of copper bar securely clamped againstthe terminals by the bolts shown in the figure. The box isprovided with a cover that is bolted against a rubber box is merely intended for coupling the ends of thecables together and takes the place of permanent joints thatcould not readily be disconnected. 25. Junction Boxes.—The main cables, or feeders,running from the station terminate in the manholes, and itis necessary to have some convenient means of connecting (T^i ^s 22L. Fig. 23. them to the various branch lines. This is done by means ofjunction boxes. Fig. 23 shows a junction box that is knownas a. four-way box, because it accommodates four positive and 20 ELECTRIC TRANSMISSION. 15 four negative cables. The box is designed for use on low-pressure, three-wire work. A and B are the positive andnegative bars, which are made of copper and are well insu-lated from each other. These bars connect across to thecable terminals through copper fuses f, so that in case ashort circuit occurs on a line, these fuses will blow and thusprevent damage. The short neutral bar shown in thebottom of the box attaches directly to the cables, because itis not usually considered necessary or even desirable to placea fuse in the neutral. The small wires p, p are pressurewires that run back to the station and there connect to volt-meters, so that the voltage at the center of distribution, repre-sented by the junction box, may be determined at any time.
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