| 摘要 |
PURPOSE:To facilitate the handling of a radio equipment without high-level technique nor qualification by specifying the transmit signal of the radio equipment within a specific band without any manual operation and thus reducing the operation contents of an operator as well as the mass. CONSTITUTION:A branch circuit 11 inputs an input signal and supplies some of it to an emphasis circuit 12. A low-pass filter 14 receives the output of the branch circuit 11 and supplies its output to a signal control circuit 15. When the output of a detecting circuit 13 increases, the signal sent from the low-pass filter 14 to a modulator 16 is cut off by the signal control circuit 15. Further, the detection output increases more and more as the frequency of the input signal is higher and higher judging from frequency characteristics of the emphasis circuit 12, so even when the amplitude of the input signal is relatively small, the cutting-off function of the signal control circuit 15 operates. When FM modulation is imposed, the band width of the transmit signal (radio wave) is wider and wider as the amplitude is larger and larger and the frequency is higher and higher, so the limit value of the amplitude should be small when the frequency is high, satisfying said condition. |
