Abstract: An explosion-proof connector of the dual envelope type having an inner waterproof neoprene connector assembly including a plug and receptacle contained in an outer explosion-proof housing including separate housing parts for the plug and receptacle. Wires of each cable connector respectively to mounting pins of the plug and receptacle and the assembled connector assembly is inserted, keyed, and locked into the outer housing with the use of at least a locking sleeve.

Abstract: The sensing device is a light level indicator that comprises a light sensitive element such as a photo resistor, associated detection circuitry and "go" and "no go" indicator lights which determine whether the level of illumination is above or below a predetermined acceptable level for a given area being tested. The device may be constructed with two light sensitive elements one for sensing direct light and the other for sensing reflected light, or alternatively, the device may have only either element. A multi-position switch may also be provided which can be set at any one of a number of different threshold levels. An adapter is used with the device for checking the calibration of the device. This adapter comprises a radioactive source, holder and a mask which is periodically replaced for maintaining the source at a constant light output.

Abstract: A rugged lighting device that is preferably for use in explosive atmosphere such as on heavy coal mining equipment has a fluorescent lighting source that is readily replaceable without requiring disassembly of the device. The lighting apparatus is constructed to operate at a very efficient high output light level even over extended periods of operation and employs either a heat sinking technique for providing this efficient operation or preferably a very high output fluorescent tube designed for high temperature operation and having an amalgam patch. The apparatus basically comprises front and rear support structures interconnected by a transparent lamp tube, a lamp assembly slideably received by the lamp tube, and a cage mounted over the support structures for protecting the lamp assembly. The front support structure is constructed to receiving electrical wiring for the lamp assembly and comprises female connector means for mating with a male connector means of the lamp assembly.