Motor vehicle with a central locking unit and a remote control for its operation

In a motor vehicle with a central locking system connected with a plurality of door locks, a remote-actuation unit including at least one transmitter acting as a key for the central locking system and having a coder, at least one receiver responsive to the transmitter and connected to the central locking system and having a decoder complementary to the coder and operating with high-frequency frequency modulation, whereby for operating the central locking system, commands are transmitted and received in a communications protocol, the improvement wherein:

• the remote-actuation unit is configured as a bandspread remote actuating device with a multiplicity of M channels and with N channels used in a frequency hopping spread spectrum mode, where (M.ltoreq.SN);
• switching is effected from one channel to another channel of the N channels in accordance with a timing pattern determined by a timing algorithm and with a certain time interval I.sub.zs ;
• the time interval I.sub.zs of the timing pattern is greater than a duration .DELTA.t of the communications protocol;
• each timing pattern of the transmitter and the receiver is determined by a respective counter setting and to establish synchronism of the timing patterns after each operation of said system the counter state of the transmitters is transferred to the receiver;
• a reference clock generator 16 provided for a carrier frequency generated by said transmitter;
• and
• said reference clock generator has a temperature compensator to maintain a precise temperature compensated clock frequency thereof.