| 摘要 |
<p>Each bidirectional sensor (BT1-BT5) that receives a message sent by a unidirectional sensor (UT1-UT2) waits for an individually-assigned time slot in order to forward it to a central control station (Z). During this time, each sensor checks that another sensor has not already forwarded the message and, if so, suppresses its own forwarding operation. All bi-directional sensors wait for the central station to acknowledge receipt of the message, otherwise, the sensors wait to forward the message. The alarm system operates with a central station (Z) and a number of bi-directional and unidirectional substations (BT, UT) connected by a radio network. The central station and the bidirectional substations can transmit and receive, while the unidirectional substations can only transmit. Unidirectional substations outside the radio receiving range of the central station try to convey messages via one of the bidirectional substations, using the following procedure : (1) the message sent by a unidirectional station is received from all bi-directional participants within radio range; (2) each bidirectional station receiving the message waits for its individually-assigned waiting period to relay the message to the central station; (3) during the waiting period, each bidirectional substation is switched to receive mode, and if a confirmation signal is broadcast from the central station forwarding of the original message from the unidirectional substation is suppressed.</p> |
