1. AN ELECTROMAGNETIC AND GATE DEVICE CONSISTING OF A SEALED REED NORMALLY OPEN CONTACT DEVICE HAVING AN ENVELOPE WITH A POLE PIECE SEALED INTO ONE END THEREOF AND AN ARMATURE SEALED INTO THE OTHER END THEREOF, A PLURALITY OF FERROMAGNETIC CORES AFFIXED TO THE EXTERNAL PORTION OF SAID POLE PIECE, AND AFFORDING BOTH A CLOSED ELECTRICAL CIRCUIT AND A CLOSED MAGNETIC CIRCUIT BETWEEN SAID POLE PIECE AND EACH OF SAID CORES, AN INPUT COIL WOUND ABOUT EACH SAID MAGNETIC CORE, SAID INPUT COILS BEING CONSTRUCTED AS SINGLE LAYER SELF-SUPPORTING COILS INTO WHICH SAID CORES MAY BE SLIPPED WHEREBY THE REED UNIT MAY BE REPLACED WITHOUT DISTURBING THE WIRING CONNECTIONS TO SAID INPUT COILS.