| 摘要 |
The system has an audio sygnal, which is to be transmitted without being tapped, applied to the input of a transmitter. The latter has a digital pulse modulator which transforms the audio signal into a digital signal. The latter is fed to an encryption, scrambling or private circuit which uses private codes to encrypt the input signal. The encrypted signal is filtered and frequency modulated for transmitting to a receiver. A substranctor in the transmitter serves to provide an error signal representative of a difference between a second analog signal, provided by analog conversion of the digital signal, and a first analog signal.
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