. The telephone system of the British post office. A practical handbook . res 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 s
. The telephone system of the British post office. A practical handbook . res 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 Relays. to ring a bell at night. It will be seen that the ends of the pole-piecesare connected by a piece of iron, which also serves to secure the electro-magnet to the base. The limbs of the electro-magnet are cased in by two C.
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Keywords: ., bookcentury1900, bookdecade1900, booksubjecttelepho, bookyear1901
