Constructional feature explosionproof and dust-ignitionproof|Factory sealed eliminates the need for adding sealing fittings and compound at each conduit entrance|The devices are enclosed in separate sealing chamber that has smooth, double flanges that mate both to the cover and mounting enclosure to provide flame-tight joints|EFD factory sealed selector switches furnished with nylon cam-operated, heavy duty pushbuttons for either 2-position or 3-position maintained contact operation|They offer high thermal and arc resistance, high dielectric strength|EFD/EFDB momentary pushbuttons are supplied with lockout type guards as standard|A hole in the guard will accept locks with up to 1/4 in hasp, permits locking of pushbutton to prevent unauthorized operation|EFD/EFDB backbox supplied with internal ground screw|Accurately tapped, tapered hubs for tight, rigid joints and ground continuity, smooth, rounded integral bushing in each hub protects conductor insulation|Corrosion resistant captive stainless steel hex head cap screws hold covers to body|Stainless steel pushbutton shaft operates within stainless steel bushing assuring long, maintece free operation|Push button and selector switch contacts are silver cadmium oxide which are sealed in lower phenolic chamber isolated from corrosive elements|Assures positive contact and long, trouble-free operation|Clearly marked terminals with brass screws assure quick, easy wiring|Pigtail leads from pushbuttons are factory sealed in sealing well|2 positions