| 摘要 |
PURPOSE:To exact an iD code from plural mobile bodies existing in a prescribed zone separately by providing a transmission means sending a call signal to a center device so as to eliminate the need for a means regulating the position of the mobile bodies. CONSTITUTION:For example, the transmission power of an antenna 22 is reduced to change the directivity into a characteristic A', then an iD code of at least a mobile body T1 is extracted. Thus, the power adjustment of the antenna 22 is required and the adjustment is executed by a control circuit 21. While the power adjustment is being increased sequentially, however, the iD code is not sent again for a prescribed time or a prescribed number of times of calls after the iD code is once sent. Then the center side completes a series of iD code collection within the time or number of times. The response control is executed in interlocking with the transmission control of the center side in this way, then it is possible to collect the iD codes of the plural mobile bodies existing in a prescribed zone separately. |
