| 摘要 |
Spread-spectrum technology, either direct sequence or frequency hopping, or a combination of the two, is used for transmitting audio signals one way and control signals two ways over an RF channel(s) to reduce interference with/from other RF transmissions and enabling use of multiple such systems in close proximity without requiring pre-selection of transmission frequencies. Alternatively, multiple channels with appended access codes may be used, wherein interference or loss of clear signal results in automatic switching to another channel. The control signals accompany the transmitted audio signal at some time in the transmission interval, or previous to the beginning of the transmission interval, and constitute a coded control message allowing a unique connection. In some cases the encoding keys may only occur at the beginning of the desired message, while in other cases the two-way control signals may continue throughout the interval of the message link.
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