| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a detection system of a squelch-tail illumination signal, capable of solving conventional problems of error detection caused by voice blocking and a reduced detection rate under weak electric signal conditions. <P>SOLUTION: In a transmission system by use of a radio transmission wave, transmitting a digital-channel guard-tone signal and a squelch-tail illumination signal for controlling unmuting or muting of an audio signal, in addition to the audio signal to be transmitted, a multistage multiple detection means employing a plurality of independent detection windows is provided for receiving and detecting the squelch-tail illumination signal. The system is so configured as to obtain a detection output of the squelch-tail illumination signal, when a predetermined number of zero-intersections is exceeded within a time length preset for the squelch-tail illumination signal in any one of the plurality of the independent detection windows. <P>COPYRIGHT: (C)2004,JPO |
