Abstract: An electrically actuated audible alarm having a magnetic structure comprising an assembly of laminations is provided to reduce eddy current losses. With the reduction of eddy current losses, faster magnetic flux buildup is possible and an increased velocity of striker and/or armature movement. The increased striker velocity permits delivery of a given quantum of energy to the gong with a reduced striker mass which in turn facilitates even greater velocity. When actuated from an a.c. current source, a diode may be used in series with the winding to interrupt magnetic flux generation on negative half cycles and permit return movement of armature and striker. Conventional interrupter contacts may be used when actuated from a d.c. source. A series diode provides for d.c. loop supervision. A multiple lead permits the audible alarm to comprise part of the loop circuit and thereby provide a supervisory signal if an audible alarm is missing.

Abstract: An improved buzzer structure is designed for automated assembly and comprises a housing, a coil wound on a bobbin, a magnetic frame, and an armature mounted for reciprocating movement between a coil core and a diaphragm. The magnetic frame includes parallel side members which mate with parallel edges of the bobbin flange for guiding and orienting the bobbin as it is inserted in the preformed frame. The frame also includes parallel top and bottom members separated by an amount slightly in excess of the bobbin height so as not to restrict bobbin insertion. The bobbin has a coupled coil terminal which mates with an arch on the frame for providing an electrical connection therebetween. An area of light pressure contact between the bobbin and frame, and starting at an intermediate point of bobbin insertion, is provided for maintaining a fixed relationship between the bobbin and the frame after the bobbin has been inserted to a predetermined relationship with respect to the frame.