| 摘要 |
<p>The invention concerns a system and a method of radio communication between a plurality of mobile units (6) and a stationary system (1, 3, 12, 14) comprising one or several transmitter units (3), wherein radio communication to one or several mobile units (6) is effected by broadcasting from one of said emitter units (3) on a first, public frequency. The stationary system further comprises a plurality of stationary receiver units (12), said units being connected to a central unit (1) via a common data communication network (14), radio communication from the mobile units (6) being effected by transmitting on a second, public frequency a burst of radio messages (25) that are receivable only by a small number of receiver units (12). From the receiver units (12) the messages are forwarded via the data communication network (14) to the central unit (1), which selects one of the forwarded messages and reads the data contained in the message. The system in accordance with the invention therefore does not require that designated communication paths be established with each communicating unit, and since only a small number of receiver units (12) receive each transmitted message, all messages may be transmitted on the same frequency. Alternative frequencies could however be utilised, for example when longer messages are to be transmitted.</p> |
