Patent ID: 6882268

Claim:
Method for keyless unlocking an access door to a closed space, in particular a motor vehicle, by means of an electronic system, comprising on the one hand a control device ( 12 ) for an electronic lock ( 14 ) for said door fitted with a first data management electronic unit ( 20 ) associated to first low frequency signal transmission means ( 24 , 25 ) and to first high frequency signal reception means ( 22 , 23 ) and on the other hand at least one portable transponder ( 16 ) comprising a second data management electronic unit ( 36 ) associated to second reception means ( 38 , 39 ) for said low frequency signals and to second transmission means ( 40 , 41 ) for said high frequency signals, said method comprising sending an interrogation signal to at least one transponder via said first transmission means and, in response, sending an identification signal via said at least one transponder to control said electronic lock, said first transmission means of said control device being activated by a signal sent by said second transmission means of said at least one transponder, characterized in that, in a preliminary operating mode of said system wherein said first transmission means are inactive, said second transmission means periodically transmits a high frequency signal for activating said first transmission means.