| 摘要 |
A mobile radio unit (3) operating in a direct mode network (1) of a TETRA (TErrestrial Trunked RAdio) network collects data from mobile radio units (4 to 6) also operating in the direct mode network (1) and, when it has received a predetermined quantity of data, or a predetermined time period has expired, it tunes automatically to the frequency of a base station (8) of the trunked network (2) of the TETRA network and listens for valid signals signifying that it is in operational range of the trunked system (2). Upon detecting the trunked network (2), the mobile radio unit (3) attempts to synchronise to a base station (8) and makes a call request to the trunked system (2) (i.e. to a despatcher (7)) via the base station (8). If the call request is accepted, the mobile radio unit (3) transfers the data it has collected to the despatcher (7) and once the data transfer is completed successfully, returns automatically to operation in the direct mode network (1) (e.g. by tuning automatically to the frequency of the direct mode network (1)), and continues to receive and store data from the mobile radio units (4 to 6), until, e.g., it is time to send further data to the despatcher (7).
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