Eddy current brake to control motor speed

Claim 1

IN AN IMAGE RECORDING AND REPRODUCING SYSTEM FOR RECORDING BROAD-BAND VIDEO SIGNALS CONSISTING OF A MAGNETIC TAPE WHICH IS LINEARLY DRIVEN BY AN ELECTRIC MOTOR, A ROTATING HEAD DRUM CONTAINING MAGNETIC TRANSDUCERS AND AN ELECTRO-MECHANICAL BRAKE APPARATUS COMPRISING MEANS FOR PRODUCING REFERENCE SIGNALS IN ACCORDANCE WITH THE ROTATION OF SAID ROTATING HEAD DRUM, MEANS FOR DERIVING CONTROL SIGNALS IN ACCORDANCE WITH SAID REFERENCE SIGNALS, MEANS FOR RECORDING SAID CONTROL SIGNALS ON ONE SIDE OF SAID MAGNETIC TAPE, AN ELECTRO-MECHANICAL BRAKE MEANS FOR CONTROLLING THE ROTATING SPEED OF SAID ELECTRIC MOTOR WHICH DRIVES SAID MAGNETIC TAPE, SAID ELECTRO-MECHANICAL BRAKE MEANS BEING OF THE TYPE UTILIZING MAGNETIC MATERIAL OF FLUID NATURE, SAID BRAKE ELEMENT BEING ENERGIZED FROM A SOURCE OF CONSTANT CURRENT SUPPLY DURING THE RECORDING OPERATION AND BY THE SIGNALS PRODUCED IN RESPONSE TO SAID ERROR SIGNALS DURING THE REPRODUCING OPERATION, FOR CAUSING SAID ELECTRO-MECHANICAL BRAKE ELEMENT TO EXERT A PREDETERMINED VALUE OF BRAKING EFFECT ON SAID ELECTRIC MOTOR ACCORDING TO THE ELECTRICAL INPUT GIVEN TO SAID BRAKE ELEMENT DURING THE RECORDING OPERATION, MEANS FOR CAUSING SAID BRAKING EFFECT TO MAKE SAID MOTOR ROTATE AT A CONSTANT SPEED DURING THE RECORDING OPERATION, MEANS FOR REPRODUCING SAID CONTROL SIGNALS RECORDED ON SAID MAGNETIC TAPE DURING THE REPRODUCING OPERATION, MEANS FOR PRODUCING ERROR SIGNALS BY COMPARING THE PHASE OF ELECTRICAL SIGNALS PRODUCED IN ACCORDANCE WITH SAID REPRODUCED CONTROL SIGNALS WITH THE PHASE OF SAID REFERENCE SIGNALS, MEANS FOR CHANGING THE ROTATING SPEED OF SAID MOTOR THROUGH CONTROLLING SAID ELECTRO-MECHANICAL BRAKE ELEMENT BY SAID ERROR SIGNALS, AND MEANS FOR CONTROLLING THE RUNNING SPEED OF SAID MAGNETIC TAPE BY SAID LAST-MENTIONED MEANS TO MAINTAIN THE NORMAL REPRODUCING OPERATION.