| 摘要 |
PURPOSE:To improve the privacy of content of communication by applying inversion and noninversion of a spectrum of a signal sent and received periodically in an equipment sending and receiving a radio signal. CONSTITUTION:A signal Ss from a subcarrier generating circuit 120 is fed to a frequency divider 122 through a switch circuit 121, a tone signal Sst is extracted from a frequency divider circuit 112 and fed to an adder circuit 117. The tone signal Sst and the signal Sti being the inversion of the spectrum are extracted from the adder circuit 117. Then the tone signal Sst, the signal Sti being the inversion of the spectrum and a signal Sto not subject to spectrum inversion are sent from a handset 1 alternately in terms of an FM signal Su. The synchronization of the inversion and noninversion is taken for the spectrum of the received signal based on the received tone signal Sst at the receiver side. Thus, the original signal is restored to a correct spectrum and extracted. |
