Electromagnetic indicator

Claim 1

AN INDICATOR FOR SELECTIVELY DISPLAYING A PLURALITY OF SYMBOLS ONE AT A TIME IN THE SAME SPACE COMPRISING: A FIRST SCREEN INCLUDING A PLURALITY OF INDICATING AND NONINDICATING PORTIONS, A SECOND SCREEN IN JUXTAPOSED RELATIONSHIP TO THE FIRST SCREEN AND HAVING INDICATING AND NONINDICATING PORTIONS, SAID FIRST AND SECOND SCREENS HAVING A PLURALITY OF DISCRETE RELATIVE POSITIONS, THE TOTAL NUMBER OR RELATIVE POSITIONS BEING A FUNCTION OF THE TOTAL NUMBER OF SYMBOLS TO BE DISPLAYED; A DIFFERENTIAL MECHANISM HAVING AN OUTPUT ELEMENT CONNECTED TO ONE OF SAID SCREENS FOR SELECTIVELY SHIFTING SAID ONE SCREEN INTO ANY ONE OF SAID PLURALITY OF POSITIONS RELATIVE TO THE OTHER SCREEN AND HAVING FIRST AND SECOND INPUT ELEMENTS DIFFERENTIALLY COUPLED TO SAID OUTPUT ELEMENT SUCH THAT AN INCREMENT OF MOVEMENT APPLIED TO SAID SECOND ELEMENT PRODUCES SUBSTANTIALLY GREATER MOVEMENT OF SAID OUTPUT ELEMENT THAN DOES THE SAME INCREMENT APPLIED TO THE FIRST INPUT ELEMENT; SAID DIFFERENTIAL MECHANISM MOVING ITS SAID OUTPUT ELEMENT ONE INCREMENT FROM A BASE POSITION IN RESPONSE TO MOVEMENT OF SAID FIRST INPUT ELEMENT THROUGH ITS FIXED DISTANCE; SAID DIFFERENTIAL MECHANISM MOVING ITS SAID OUTPUT ELEMENT A DISTANCE SUBSTANTIALLY GREATER THAN SAID ONE INCREMENT BETWEEN DIFFERENT BASE POSITIONS IN RESPONSE TO MOVEMENT OF SAID SECOND INPUT ELEMENT THROUGH ITS FIXED DISTANCE.