. American telephone practice . the actual devices and apparatusused in the protection of telephone equipments and lines, the matterof fuses will be first considered. One of the usual forms of sneakcurrent fuses is that shown in Fig. 424, this being known as theWestern Union type. Another common fuse differing only in thestyle of its terminals is shown in Fig. 428, this being known asthe Postal type. The salient points of difference between the Western Union andthe Postal fuses is that the former is adapted to insertion betweenspring clips, while the latter is secured in place on its clipsby c
. American telephone practice . the actual devices and apparatusused in the protection of telephone equipments and lines, the matterof fuses will be first considered. One of the usual forms of sneakcurrent fuses is that shown in Fig. 424, this being known as theWestern Union type. Another common fuse differing only in thestyle of its terminals is shown in Fig. 428, this being known asthe Postal type. The salient points of difference between the Western Union andthe Postal fuses is that the former is adapted to insertion betweenspring clips, while the latter is secured in place on its clipsby cross screws extending through the slots in its ends. Thesefuses are, as a rule, adapted to inside construction only. If, there-fore, they are placed outside, they should be inclosed in weather-proof boxes of substantial character. Such fuses are often mounted in conjunction with carbon arrestersso as to form protection against both low potential and high poten-tial currents, the theory of such operation and connection with the. FIG. 428.—WESTERN UNION FUSE. line circuit being the same as described in connection with Such a combination adapted to a single line wire is shownin Fig. 429, which, as will be seen, employs the Postal type of two carbon blocks of this figure are adapted to be held in thespring clips shown at the upper portion of the porcelain base, themica washer serving to keep them from actual electrical metallic circuit lines these devices are usually made up in pairs,mounted on porcelain blocks, there being one fuse and carbon ar-rester for each side of the line. In Fig. 430 such a device for ametallic circuit adapted to use with Western Union fuses is shown,while that in Fig. 431 employs the same combination adapted toPostal type In Fig. 432 is shown one of these combinedcarbon and fuse arresters applied to a line circuit entering an ordi-nary magneto-telephone. This practice is used in many countryexchanges, and as a cheap
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