Electromagnetic electroacoustic transducer

Claim 1

AN ELECTROMAGNETIC ELECTROACOUSTIC TRANSDUCER, WHICH COMPRISES A CENTRAL PLUG OF PERMANENT-MAGNETIC MATERIAL GENERATING A PERMANENT MAGNETIC FLUX AND HAVING TWO MUTUALLY OPPOSITE END FACES, POLE MEANS COMPRISING TWO POLE PLATES, EACH OF WHICH CONTACTS ONE OF SAID END FACES AND THE DIAMETERS OF WHICH ARE SUBSTANTIALLY EQUAL TO THEMSELVES AND LARGER THAN THE DIAMETER OF SAID PLUG, SAID POLE PLATES DEFINING BETWEEN THEMSELVES A FREE SPACE, SAID POLE MEANS DEFINING AN OUTER AIR GAP AND AN INNER AIR GAP, AN ARMATURE OF MAGNETIC MATERIAL IN THE SHAPE OF A CIRCULAR RING EXTENDING THROUGH SAID OUTER AIR GAP WITH FREEDOM OF VIBRATION THEREIN ADN HAVING AN INER RIM DISPOSED IN SAID INNER AIR GAP, SAID TRANSDUCER COMPRISING FURTHER ANNULAR ARMATURE RETAINING MEANS OF NONMAGNETIC MATERIAL ENGAGING SAID INNER RIM OF SAID ARMATURE ON BOTH SIDES THEREOF IN SAID INNER AIR GAP TO RETAIN SAID ARMATURE, SAID ARMATURE HAVING AN OUTER RIM DISPOSED RADIALLY OUTWARDLY OF THE PERIPHERY OF SAID POLE MEANS, SAID TRANSDUCER COMPRISING FURTHER A DIAPHRAGM SECURED TO SAID OUTER RIM OF SAID ARMATURE AND ADAPTED TO VIBRATE AT SOUND FREQUENCIES, AND AN EXCITER WINDING WHICH IS DISPOSED IN THE INTERIOR OF SAID TRANSDUCER AND CONCENTRIC WITH THE AXIS THEREOF AND ADAPTED TO GENERATE AN ALTERNATING MAGNETIC FLUX PERMEATING SAID ARMATURE WHERE IT EXTENDS THROUGH SAID OUTER AIR GAP.