Electronic combination lock

Claim 1

AN ELECTRONIC COMBINATION LOCK COMPRISING A LATCH ACTUATOR, A POWER SUPPLY, A CONTROL CIRCUIT FOR SELECTIVELY FEEDING OPERATING POWER FROM SAID SUPPLY TO THE LATCH ACTUATUR, SAID CONTROL CIRCUIT COMPRISING A PLURALITY OF SEMICONDUCTOR BISTABLE DEVICES EACH HAVING AN OUTPUT ELECTRODE, AN INPUT ELECTRODE, AND A CONTROL ELECTRODE, SAID BISTABLE DEVICES BEING IN ONE CONDUCTIVE STATE AND ARRANGED IN CASCADE SUCH THAT THE OUTPUT ELECTRODE OF ONE BISTABLE DEVICE IS COUPLED TO THE INPUT ELECTRODE OF THE NEXT SUCCEEDING BISTABLE DEVICE, EACH SAID BISTABLE DEVICE BEING OPERABLE TO THE OTHER CONDUCTION STATE ONLY WHEN THE NEXT PRECEDING BISTABLE DEVICE IS IN THE OTHER CONDUCTION STATE AND AN OPERATING SIGNAL IS RECEIVED BY THE RESPECTIVE CONTROL ELECTRODE, EACH BISTABLE DEVICE RETURNING TO SAID ONE CONDUCTION STATE WHENEVER THE NEXT PRECEDING BISTABLE DEVICE RETURNS TO SAID ONE CONDUCTION STATE, A BISTABLE FIRST STAGE HAVING ITS OUTPUT CONNECTED TO THE INPUT ELECTRODE OF THE FIRST BISTABLE DEVICE AND NORMALLY FEEDING A DISABLING VOLTAGE THERETO TO MAINTAIN SAID FIRST BISTABLE DEVICE IN SAID ONE CONDUCTION STATE, SAID FIRST STAGE HAVING A CONTROL ELECTRODE AND AT LEAST ONE RESET ELECTRODE, A PLURALITY OF OPERABLE BUTTON SWITCHES COUPLED TO SAID POWER SUPPLY FOR PASSING SIGNALS WHENEVER THE BUTTON SWITCHES ARE OPERATED, ADJUSTABLE COUPLING MEANS FOR CONNECTING DIFFERENT ONES OF A GROUP OF SAID BUTTONS TO DIFFERENT ONES OF SAID CONTROL ELECTRODES AND FOR CONNECTING ONE OF SAID BUTTON SWITCHES TO THE CONTROL ELECTRODE OF SAID FIRST STAGE SO THAT WHENEVER THE PRECEDING FIRST STAGE OR BISTABLE DEVICE CHANGES TO THE OTHER CONDUCTION STATE AND A SIGNAL IS RECEIVED BY THE NEXT CONTROL ELECTRODE ASSOCIATED WITH A PARTICULAR BUTTON