or connected in parallel across the line, and are not connected in series. If one telephone should get out of order, the others are not likely to be disabled. Figs. 8 and 9 show the system of wiring and installation used by the StrombergCarlson Telephone Manufacturing Company. It will be noted that there is a metallic circuit for the telephones separate and distinct from that used for either lighting or emergency bells. Fig. 10 shows the combined telephone and emergency (alarm) system of bells employed by the Western Electric Company, in which three wires are used. As in the case shown in Fig. 8, a separate generator is employed to ring the alarm bells. One of these is installed at some central point on the surface where some one is always on duty to receive telephone calls from points inside the mine and, if necessary, to sound the alarm bells. Other generators may be installed at other points, say, at the foot of the shaft or at the inside parting, from which it may be desirable to be able to send warning signals in event of accident. Fig. 11 shows a complete bell annunciator and telephone outfit as installed in one of the anthracite mines of the D., L. & W. R. R. Co. Bridging instruments are used and each bell in the shaft is provided with a return-call button. This bell wiring should be put up in a substantial manner, and it is best, if possible, to run all the wires down the shaft in the shape of a lead-covered cable. Another shaft-signaling apparatus is shown in Fig. 12, as used at the West Vulcan mines, Mich. Fig. 13 shows a form of waterproof push button used at the same mine. Fig. 14 shows the arrangement of flash signals as used in Montana. This consists of a switch cut into a lighting circuit at each level of the mines. By pulling out the handle bar of the switch, all the lights on this circuit can be flashed at once, and by a properly arranged code of flash signals, the system can be used for communicating between the surface to any part of the mine, and between different portions of the mine. 18T. LEVEL 2ND LEVEL 3RD. LEVEL 4TH. LEVEL 6TH. LEVEL 6TH. LEVEL FIG. 11 |