Abstract: An optical block for the exciter lamp and photocell includes a base with a first seat holding the lamp on a first optical axis and a second seat holding the cell on an intersecting optical axis. A cover with two light passages along the axes has a socket into which the base snap fits to confine the lamp and cell in their seats.

Abstract: A smoke detector receiving at two input terminals DC power from a remote source not only gives an alarm indication in response to a significant density of smoke, but senses the polarity of DC power at the terminals and generates a secondary signal, distinguishable from the alarm signal, when the polarity of power source is reversed.

Abstract: An optical smoke detector has an optical block canopied by a substantially broad surfaced wall member that is pivotally attached to the opposite sides of the optical block and substantially spaced from the active surface of the optical block itself such that the sides of the wall member are open to stray ambient light. Manual owner-test-actuation of the alarm is accomplished by depressing an externally extending push-button which in turn gradually moves the wall member inwardly of the optical block. The gradual and consequent decrease in reaction volume between the light scattering surface of the moving wall member and the optical block, the optical block housing an infrared light emitting diode and an infrared photosensitive cell, creates a simulated atmosphere of smoke infiltration so as to cause an associated alarm circuit to be innervated.

Abstract: A mounting bracket having multiple bayonet coupling elements which interengage with the bayonet coupling elements located on the body of an electrical instrument to be attached to a junction box. Additionally and in combination with the bayonet coupling elements, on the bracket and instrument body respectively, are included a pawl and ratchet arrangement for providing fine rotational adjustment while a toothed spring finger attached to the bracket engages a notched annular wall on the instrument body so as to latch and further secure the bracket to the body. It is anticipated that the mounting bracket will have to be attached to any one of several types of junction box thereby necessitating a multidirectional coupling arrangement for properly attaching the subject instrument to the particular junction box encountered.

Abstract: A photoelectronic smoke detector has walls around a dark chamber to which smoke, but not light, is admitted, and through which light is directed from an exciter light source on a path to a limited area of a chamber wall. A first photocell views light scattered from the through path by particles in the path primarily to produce an alarm signal, and also receives background light scattered from the chamber wall outside the limited area. A second photocell is disposed to receive background light substantially only from the limited area and other areas outside the source light path. The first cell produces a first signal in response to background and particle-scattered light. The second cell produces a second signal corresponding to background scatter. The first and second cells, preferably photovoltaic photodiodes, are coupled in opposition in a circuit whose output consequently is substantially independent of the background light.

Abstract: An optical smoke detector including a plurality of walls extending from a dark chamber in which an optical smoke sensor is located. The walls form passages in the detector which extend from smoke entrances on the outer perimeter to smoke ports that feed into the dark chamber. In construction, the smoke entrances extend substantially continuously around the perimeter of the smoke detector to allow the free entry of smoke into the dark chamber. Each wall is arranged to overlap the next so as to obstruct the direct rays of light from entering the dark chamber and a screen is disposed around the perimeter of the detector to prevent the entrance of insects into the dark chamber.