| 摘要 |
A path along which a vehicle traverses is divided into a plurality of blocks. In each block two devices sense the presence of a vehicle, and one of the devices is used to sense the absence of the vehicle. The two devices concurrently sensing the presence of a vehicle provide a presence signal to be stored which is indicative of a vehicle having been present in the block. In response to the sensing of the absence of the vehicle by the one device during the time the presence signal is stored, a control signal is generated. A predetermined amount of time after the control signal is generated the storage of the presence signal is discontinued.
|
