| 摘要 |
In order to make invisible from the outside the coding of a keycard having magnetically readable information points and to prevent copying or modifying without destruction, while authorizing the reading thereof without moving parts, there is provided a plate (3) covered on both sides with plates (1, 2) of non-magnetizable material in the introduction direction with a plurality of cut-out holes (4) interarranged according to a key system for the magnetic reading and identification. The plate is made either of magnetizable material or of non-magnetizable material, the holes being in this case filled with a ferromagnetic substance (3a) according to a predetermined coding. To enable the introduction of the right side of the keycard into the lock, the edges of both covering plates are secured to each other in the plane of one of the covering plates and form on a front side a mouthpiece (7) of special shape. To each row of holes there is adjoined a reading head comprising a permanent magnet (9) directed to the rows of holes, of which the magnetic field lines are modified according to the introduction position of the keycard into the lock by means of the change between the air and the metal. This results in sudden modifications of the magnetic induction which is transformed by a measurement value converter (6) like a field plate into electric control and count pulses before it is supplied to an evaluation circuit. |
