1. A SINGLE-ACTION TEMPERATURE-SENSITIVE ELECTRICAL SWITCH COMPRISING: AN ELONGATED HOUSING HAVING A TRANSVERSELY SPACED PAIR OF ELECTRICAL TERMINALS IN THE INTERIOR OF ONE END THEREOF; A PLUNGER IN THE MID-PORTION OF SAID HOUSING ADAPTED TO SLIDE TOWARD SAID TERMINALS FOR PRODUCING AN ELECTRICAL SWITCHING ACTION; MEANS WITHIN THE OTHER END OF SAID HOUSING PROVIDING A PELLET CHAMBER HAVING AN OPENING FACING TOWARD SAID PLUNGER, AND HAVING AN INTERIOR SHOULDER FACING AWAY FROM SAID OPENING; A SPRING BIASING SAID PLUNGER FOR MOVEMENT TOWARD SAID TERMINALS; A RESILIENT SPRING RETAINING MEMBER HAVING ONE END FASTENED TO SAID PLUNGER, ITS OTHER END EXTENDING THROUGH SAID OPENING INTO SAID PELLET CHAMBER AND HAVING AN OFFSET PORTION WHICH HOOKS OVER SAID SHOULDER; A TEMPERATURE-SENSITIVE PELLET OCCUPYING SAID PELLET CHAMBER AND COMPRESSIVELY ENGAGED BY SAID SPRING RETAINING MEMBER FOR MAINTAINING THE ENGAGEMENT OF SAID OFFSET PORTION OF SAID MEMBER WITH SAID SHOULDER; AND MEANS FOR APPLYING HEAT TO SAID PELLET FROM THE EXTERIOR OF SAID HOUSING TO MELT SAID PELLET, SAID OFFSET PORTION OF SAID MEMBER AND SAID SHOULDER TOGETHER THEN PROVIDING A CAM ACTION FOR FORCING SAID OTHER END OF SAID MEMBER RADIALLY INWARDLY OF SAID CHAMBER AS SAID PLUNGER MOVES TOWARD SAID TERMINALS.