| 摘要 |
In a radio frequency communications system, a data carrier activation method is implemented such that the carrier is switched off when no data is available for transmission. If repeated signalling information is required to be transmitted, only a predetermined number of repeats is transmitted before the carrier is switched off. The data input for transmission are compared with an idle sequence with different bit alignments to detect the presence of idle signalling, and the carrier is switched off if a match is found. When more user data is received, the carrier is switched on and frames (SM) are transmitted in synchronization with the timing of frames (SM) transmitted before the carrier deactivation. After carrier reactivation, a constant power preamble (P) may be transmitted to assist in level control in the transmitter (27; 40).
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