| 摘要 |
A monitoring apparatus and a method of monitoring a zone are disclosed. A plurality of beams (14) are transmitted between at least two locations (12.2,12.2) defining extremities of the zone. Interruptions of the beams (14) caused by an object moving between the two locations are detected by sensing means and a graph of the interruptions relative to time is generated. The graph generated is compared with a set of preselected graphs representative of known objects stored in storage means (34). <IMAGE> |
