. The telephone system of the British post office. A practical handbook . The switch-springs consist of two springs Sj and Sj (Figure 45), restingupon two contact points, A and B. The upper spring S^ is cleft in order topermit the insertion of the peg. The springs curve backwards, and arefitted upon the back of the bo,ard by means of Figure 46. The pegs consist of two flat pieces of flat brass A and B (Figure 46)insulated by ebonite, fitted with a handle. One of the brass pieces carriesa projection P, which fits the cleft in the upper brass spring. Thisensures that the peg shall be in
. The telephone system of the British post office. A practical handbook . The switch-springs consist of two springs Sj and Sj (Figure 45), restingupon two contact points, A and B. The upper spring S^ is cleft in order topermit the insertion of the peg. The springs curve backwards, and arefitted upon the back of the bo,ard by means of Figure 46. The pegs consist of two flat pieces of flat brass A and B (Figure 46)insulated by ebonite, fitted with a handle. One of the brass pieces carriesa projection P, which fits the cleft in the upper brass spring. Thisensures that the peg shall be inserted the right way up, and this, as willbe seen later, is an important matter. The indicator employed consists of an electro-magnet C and C(Figures 47 and 48), in front of which is a circular iron ring R, pivoted at itslower extremity. Between the two poles of the electro-magnet a magnetisedneedle N is hung. The protruding iron cores are covered with ebonite, inorder that the needle may not stick to the pole pieces. The back of theiron shutter is covered with paper, in order to prevent its sticking—due to residual magnetism. When the shutter drops, the small insulatedspring S is brought into contact with the pin P, which is connected to thebase or brass foundation of the instrument, and this contact is employed 6o Indicators and R
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelepho, bookyear1901
