Error-correcting typewriter

Claim 1

A TYPEWRITER FOR USE WITH RIBBONS PROVIDING A PRINTING FIELD AND A PRINT-OBTAINING FIELD, SAID TYPEWRITER INCLUDING CHARACTER-PRINTING MECHANISM, A PAPER SUPPORT MECHANISM, PRINTING CONTROL KEYS, SPACING MEANS FOR STEPWISE MOVING SAID MECHANISMS RELATIVE TO ONE ANOTHER IN A FORWARD DIRECTION TO ACCOMPLISH PRINTING OF A LINE OF CHARACTERS, A RIBBON VIBRATOR ACTUATED BY THE PRINTING CONTROL KEYS TO BRING A RIBBON FIELD MOMENTARILY INTO OPERATIVE POSITION UPON ACTUATION OF EACH OF SAID PRINTING CONTROL KEYS, RIBBON FIELD-SELECTING MEANS FOR CONTROLLING THE EXTENT OF MOTION OF THE VIBRATOR TO SELECT THE PARTICULAR RIBBON FIELD THAT IS THUS BROUGHT INTO OPERATIVE POSITION, BACKSPACE DRIVE MEANS FOR STEPWISE MOVING SAID MECHANISMS RELATIVE TO ONE ANOTHER IN THE BACKWARD DIRECTION IN LETTER-WIDTH INCREMENTS, A PAIR OF BACKSPACE KEYS BOTH CONNECTED TO OPERATE SAID BACKSPACE DRIVE MEANS, CONNECTIONS BETWEEN SAID BACKSPACE KEYS AND SAID FIELD-SELECTING MEANS TO SHIFT THE LATTER BETWEEN POSITION RESPECTIVELY CORRESPONDING TO THAT BACKSPACE KEY WHICH WAS LAST OPERATED, AND MEANS FOR SELECTIVELY DISENGAGING SAID CONNECTIONS, TO PERMIT THE USE OF SAID BACKSPACE KEYS WITHOUT ALTERING THE RIBBON-FIELD SELECTION.