| 摘要 |
PURPOSE: To keep the number of traveling objects contained in a communicable area always and substantially one to solve the problem of interference by measuring the traffic of traveling objects and setting the size of the communicable area on an interrogator variable in accordance with this result. CONSTITUTION: A vehicle sensor 20 detects the speed of a passing vehicle by using an ultrasonic sensor, etc. A traffic measuring instrument 30 measures the traffic of the vehicle passing through a road by totaling the speed signal of the vehicle sensor 20 at every definite period of time. Then, the measured result is sent to the output (power) variable circuit 11 of an interrogator 1 side, and controls transmitter power to be transmitted from a transmission system 12. The traffic of the traveling object is measured, and the size of the communicable area of the interrogator is set variable in accordance with the measured result in this way. Thus, the traffic of the traveling object is measured, and the number of the traveling objects contained in the communicable area is kept always and substantially one, and the problem of the interference is eased. |
