A. c. motor servo mechanism for tape transports

Claim 1

IN A TAPE TRANSPORT FOR DIGITAL RECORDING APPARATUS, A PAIR OF TAPE STORAGE REELS ADAPTED TO RECEIVE A SUPPLY OF TAPE FOR THEREBY DISPENSING AND TAKING-UP EXCESSIVE TAPE, ALTERNATING CURRENT MOTORS COUPLED TO DRIVE EACH OF THE STORAGE REELS, MOTOR SWITCHING CIRCUITS FOR MAINTAINING EACH MOTOR INDEPENDENTLY IN ENERGIZED OR DEENERGIZED STATE WHEN RECEIVING CORRESPONDING CONTROL SIGNALS, TRANSDUCING MEANS, TAPE DRIVE MEANS FOR ADVANCING TAPE INCREMENTALLY PAST THE TRANSDUCING MEANS INDEPENDENT OF MOTION OF THE STORAGE REELS, A FIRST TAPE LOOP LENGTH DETECTION MEANS INCLUDING TWO LIMIT SWITCHES SPACED FOR MOMENTARY CONTACT AT EACH LIMITING END POSITION OF A RANGE OF TAPE LOOP LENGTH FOR CONTROLLING THE DISPENSING OF TAPE FROM ONE OF THE REELS BY THEREBY PRODUCING CONTROL SIGNALS FOR SAID MOTOR SWITCHING CIRCUITS AND ENERGIZING THE RESPECTIVE MOTOR WHEN THE LOOP LENGTH REACHES ONE LIMIT POSITION AND HOLDING THE MOTOR ENERGIZED WHEN THIS CORRESPONDING LIMIT SWITCH OPENS UNTIL THE OTHER LIMIT SWITCH IS CONTACTED THEREBY DE-ENERGIZING THE MOTOR WHEN THE LOOP LENGTH DEPARTS FROM A PREDETERMINED RANGE, AND A SECOND SIMILAR TAPE LOOP LENGTH DETECTION MEANS INCLUDING LIMIT SWITCHES FOR CONTROLLING THE TAKE-UP OF TAPE ON THE REMAINING REEL BY THEREBY ENERGIZING ITS MOTOR WHEN THE LOOP LENGTH REACHES A LIMIT POSITION AND DE-ENERGIZING THE MOTOR WHEN THE LOOP LENGTH DEPARTS FROM A PREDETERMINED RANGE, AND MEANS RETAINING A RELATIVELY CONSTANT TENSION ON THE TAPE THROUGHOUT SAID RANGE, WHEREBY EACH MOTOR IS INTERMITTENTLY OPERATED TO TRANSPORT A PREDETERMINED AMOUNT OF TAPE WHILE PERMITTING INDEPENDENT HIGH SPEED INCREMENTAL PROCESSING OF THE TAPE PAST THE TRANSDUCING MEANS.