Abstract: An electrical plug and receptacle can be connected and disconnected in the presence of explosive gas without causing a spark and possible explosion. Power is disconnected from the receptacle unless the plug is fully inserted and locked into position in the receptacle. A sensor detects when the plug is fully inserted and locked. The sensor energizes a relay which allows power to flow to the receptacle and the connected plug. The relay is encapsulated in epoxy or isolated in a Restricted Breathing enclosure to keep explosive gas away from the sparking relay contacts. To remove the plug from the receptacle, it must first be unlocked. The sensor detects the motion of unlocking the plug and releases the relay to disconnect power from the plug and receptacle so that no spark is created when the plug is removed from the receptacle. Ordinary NEMA plugs and receptacles can be used in Zone 2 and Class I Division 2 hazardous locations.

Abstract: An electrical apparatus, comprises a restricted breathing enclosure having an interior cavity, and a temperature regulator having at least an interior sensing portion within the interior cavity, the temperature regulator including a processor responsive to the interior sensing portion to send control signals to a heat transfer portion of the temperature regulator.

Abstract: An electrical apparatus, comprises a restricted breathing enclosure having an interior cavity, and a temperature regulator having at least an interior sensing portion within the interior cavity, the temperature regulator including a processor responsive to the interior sensing portion to send control signals to a heat transfer portion of the temperature regulator.

Abstract: Communicating relative to a subterranean well includes encoding information in an amplitude and a duration for a pulse. A detectable change in response to both the amplitude and duration communicates the information. Two distinct items of information can be encoded wherein the information encoded in the amplitude is distinct from the information encoded in the duration. A single, more highly resolved, item of information can be defined in that the amplitude and the duration can together represent one aspect of the information to be communicated. Particular application is found in a subterranean well having three-phase power conductors connected to a three-phase motor in the well with the amplitude and duration being communicated through the power conductors.