An important feature in polarized bells is the adjustment between the armature and the pole pieces. This is secured in the Western Electric bell by means of the nuts 7, by which the yoke 4 is secured to the standards 3. By moving these nuts up or down on the standards the armature may be brought closer to or farther from the poles, and the device affords ready means for clamping the parts into any position to which they may have been adjusted.

Fig. 79. Polarized Bell
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Kellogg Ringer. Another typical ringer is that of the Kellogg Switchboard and Supply Company, shown in Fig. 80. This differs from that of the Western Electric Company mainly in the details by which the armature adjustment is obtained. The armature supporting yoke 1 is attached directly to the cores of the magnets, no supporting side rods being employed. Instead of providing means whereby the armature may be adjusted toward or from the poles, the reverse practice is employed, that is, of making the poles themselves extensible. This is done by means of the iron screws 2 which form extensions of the cores and which may be made to approach or recede from the armature by turning them in such direction as to screw them in or out of the core ends.

Fig. 80. Polarized Bell
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