The practical telephone handbook and guide to the telephonic exchange (1906)
Poole, Joseph · New York, Macmillan Co. · leaf 202
s.Nos. 4 and 5 are not allowed to go through to the exchange, SMALL SWITCH-BOARDS 177 and are fitted with 2-point plugs, and the bush and longestspring are joined together. It results from these connec-tions that the service instrument and Nos. 1, 2, and 3 linescan be connected to any other lines,… … Fig. 203 the sleeve of the plug, and the tip spring is already connectedto the bush. A similar effect is produced if the exchangeplug is inserted in a private line-jack (Nos. 4 and 5). Double-cord boards may also be arranged for mixed service.3-point plugs and cords are then used, the short or tip…
Telephone
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