| 摘要 |
Each of a set of two ignition keys 21 has an RF transmitter unit 22 attached to it for transmitting coded signals to the control unit 10 of a passive re-mobilise type of security system. The units 22 of a set respond differently to the control unit 10, eg after a different number of pulses from coil 34 to ensure that simultaneous command signals cannot be transmitted from both transmitter units. The transmitter units 22 may be produced in large numbers without security codes but carrying an identifying number in their memories according to whether they are the first or the second of the set of two. The transmitter units 22 are then sorted into two groups by these identifying numbers. To make a set of units 22 for an individual vehicle, one unit is taken from each group and a security code specific to the vehicle is put into the pair of units. During this procedure, the vehicle's security control unit 10 checks the numbers of the units 22 and stops the matching if the numbers are the same eg by warning the person carrying out the matching or by refusing to accept the duplicated number.
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