Abstract: A buzzer structure, of the type comprising a housing having a coil unit therein and an armature mounted for vibratory movement adjacent the coil unit, includes in one embodiment an integral portion of the housing which is bent inwardly into engagement with the coil unit to fix the spacing between the coil unit and housing, thereby to determine the dimensions of the gap between the coil unit and armature. In a further embodiment, the coil unit is mounted directly to a deformable, integral part of the housing which is bent inwardly to fix the spacing between the coil unit and an adjacent diaphragm.

Abstract: Smoke detection apparatus including a pair of photoelectric cells which receive illumination selectively from a very low level light source. One of the cells is termed the "direct" cell because it is in the direct path or on the axis of a narrow conical beam of light emanating from the source, the other cell being termed the "reflected" cell because it receives a significant part of its light input upon reflection of light from smoke particles or the like as such particles are drawn into the path of the light beam. Under predetermined smoke conditions, i.e., when there is smoke obscuration of the light of 2% per foot (.01 optical density), an alarm signal is triggered. The very low level light source is a light-emitting diode which sensitively monitors the smoke obscuration; only a slight change in the illumination to the pair of photocells, connected in a sensing circuit, is required to produce the triggering signal.

Abstract: An electronic circuit including a transistor which is biased to conduction is provided to initiate actuation of an electromagnetic transducer. The transducer has first and second coils one of which actuates the sounder. A potential is induced in the other coil and this induced potential is used to cut off the transistor. The next cycle of operation is initiated when the induced potential falls below a predetermined value in response to the reduction of the magnetic flux which, in turn, was the result of the transistor having been cut off.