Electronic multistage coded key - with semiconductor circuit actuated by input pulses has capacitor for erasing of actuating capability after time lapse

摘要

On applying an input pulse a circuit produces an output signal when the individual circuits are actuated in a previously specified sequence or by electronic means. The coding stage of this kind is available for actuation only for a certain period after actuation. After this time has elapsed a relevant actuating pulse does not produce any results. This means that the actuating capability is automatically erased. Only the first code stage is excepted and can be actuated at any time. This arrangement ensures that the electronically actuated key code cannot be broken by repeated testing. Each coding stage consists of only one transistor together with the associated base and collector resistors and coupling capacitor which is connected between the collector of the previous stage and the base. No transistor is used in the first stage. The last stage is connected to a power transistor for reliable releasing of the locking solenoid.