NON OF THE MACHINES THAT I HAVE EVER SEEN HAD SUCH A TUBE KEYER... WEIRD, MAKES YOU WONDER HOW AND WHY THE MACHINES THAT HAD THE TUBE DIFFER FROM THE ONES OUT HERE IN SO. CAL... JUST AN OBSERVATION... SEEMS THOUGH THAT THE TUBE KEYER WOULD GENERATE NO NOISE AS MIGHT THE POLAR RELAY UNIT... BUT DOES ONE REPLACE THE OTHER???