The invention relates to a method for establishing whether or not a first person who has identified himself for entrance to a confined space or area with the aid of a magnetic card inserted in a card reader (7) shall be granted free passage to the confined area through a door, gate or like entrance. The card reader (7) evaluates a code significant to the magnetic card and, through the intermediary of electric and/or electronic circuits compares the code with a plurality of pre-stored codes (12) and causes a signal to be generated for deactivating a circuit (2) for latching the door, gate or like entrance when, and only when, acceptable agreement is found between the sensed magnetic card code and the prestored codes, to therewith afford free passage to said person. The method is mainly characterized in that: a) A second person responsible for monitoring the persons desiring entrance to the confined space or area activates (6) means (16) incorporated in the electric and/or electronic circuit so that a code significant of a magnetic card subsequently sensed in the card reader (7) can be stored among a number of pre-stored codes (12); b) The second person identifies the first person and establishes the validity of a magnetic card in the possession of the first person, the magnetic card being intended for other main purposes than that of obtaining entrance to the confined space or area; c) The magnetic card belonging to the first person is inserted into the card reader (7) which senses the code significant to the card; d) The significant code is therewith stored as an additional code among pre-stored codes (12), and in that e) a subsequent sensing of the magnetic card in the card reader (7) affords free access to the confined space or area.
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