| 摘要 |
A UHF carrier signal modulated by a video signal, where the frequency and the format of a line synchronisation signal are known, is transmitted in a transmission region (1) in a confined medium by a microwave link. In a reception region, two signals are received along two angularly offset privileged axes, each is frequency-demodulated along identical processing channels, the existence in the signal emitted from one of the channels, the ''starting channel'', of a periodic signal with the line synchronisation frequency is checked and this signal is selected if the check proves positive. If the periodic signal disappears, the test is applied to the other channel; if that check is positive, this other channel is selected until this periodic signal disappears, and so forth. Such a process is especially applicable in tunnels.
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