Arming switch for selective firing systems

Claim 1

FOR USE IN PERFORATING APPARATUS INCLUDING A HOUSING HAVING A BORE THEREIN, AN ARMING SWITCH COMPRISING: A MOVABLE ELECTRICALLY-CONDUCTIVE PLUNGER MEMBER ADAPTED FOR RECEPTION IN THE BORE AND ARRANGED FOR TRAVEL THEREIN BETWEEN FIRST AND SECOND LONGITUDINALLY-SPACED POSITIONS IN RESPONSE TO A PRESSURE FORCE AT ONE END THEREOF; AN ELECTRICALLY-CONDUCTIVE MEMBER MOUNTED ALONG A PORTION OF SAID PLUNGER MEMBER AND ARRANGED TO BE SPACED FROM THE WALLS OF THE BORE; MEANS ON SAID PLUNGER MEMBER FOR PROVIDING ELECTRICAL INSULATION BETWEEN SAID PLUNGER MEMBER AND SAID CONDUCTIVE MEMBER AND HOUSING CONSISTING OF AN ELECTRICALLY NONCONDUCTIVE SURFACE ALONG THOSE PORTIONS OF SAID PLUNGER MEMBER WHICH CONTACT THE HOUSING AND SAID CONDUCTIVE MEMBER; AND FIRST AND SECOND ELECTRICAL CONTACT MEMBERS ADAPTED FOR LONGITUDINAL SPACING FROM ONE ANOTHER AND ARRANGED FOR SAID FIRST CONTACT MEMBER TO ELECTRICALLY CONTACT SAID PLUNGER MEMBER WHENEVER SAID PLUNGER MEMBER IS IN SAID FIRST POSITION AND FOR SAID CONDUCTIVE MEMBER TO ELECTRICALLY INTERCONNECT SAID CONTACT MEMBERS WHENEVER SAID PLUNGER MEMBER IS IN SAID SECOND POSITION; AND MEANS ON ANOTHER PORTION OF SAID PLUNGER MEMBER ADAPTED FOR ESTABLISHING AN ELECTRICAL PATH INCLUDING SAID PLUNGER MEMBER AND SAID FIRST CONTACT MEMBER WHENEVER SAID PLUNGER MEMBER IS IN SAID FIRST POSITION.