| 摘要 |
PROBLEM TO BE SOLVED: To prevent received data from being omitted or misdetected by setting up the receiving sensitivity to different values in accordance with the fitting position of an on-vehicle antenna and the sort of the vehicle. SOLUTION: A relay antenna cable 23 is connected between an antenna cable A 21 connected to an on-vehicle antenna 1 and an antenna cable B 22 connected to a control unit 3. The cable A 21 is connected to one side of the cable 23 and the other side of the cable 23 is connected to the cable B 22. Plural relay antenna cables 23 having respectively different loss values are prepared. When the intensity of a receiving electric field is lower than a set reference value, a relay antenna cable 23 having a low loss value, e.g. a cable of short cable length, is selected. When the intensity is higher than the reference value, a relay antenna cable 23 having a high loss value, e.g. a cable of long cable length, is selected so as to be able to lower the intensity level of the receiving electric field.
|
