Adjustable AC telephone bell system - uses bent wire as spring whose effective strength is adjusted by proper bending

摘要

An AC bell is used in telephone instruments with a vibrating armature. Each of its end positions is influenced by a permanent magnetic field and by a flexural flat spring attached to its end. The spring (14) is made of wire with its free end (15) bent nearly perpendicular to the plane of movement of the armature (1) with which it makes contact, and its middle part (18) running nearly parallel to the radius of movement of the armature. The other end (19) is held by a fixed support (20). The arrangement is preferably to known systems with flat springs since the equivalent hardness of the spring can easily be adjusted by adjustment of the degree of bending.