| 摘要 |
<p>In the transmission of information in first and second carrier frequency systems occupying the same frequency bands and each composed of a succession of channel carriers having different respective frequencies, each channel carrier defining a respective transmission channel and being modulated with a premodulation carrier itself modulated with information to be transmitted in its associated channel, at least one channel of the first system is switched into a selected channel of the second system by shifting the frequency of the modulated channel carrier of the one channel of the first system with the aid of an unmodulated channel carrier, filtering the channel to be switched through out of the shifted signal by means of a bypass filter, and converting the filtered-out channel to the frequency of the selected channel of the second system with the aid of a carrier at the frequency of a selected channel carrier of the first system.</p> |
