| 摘要 |
PURPOSE:To make the tonal signal tone soft and easy to hear, by processing and outputting the tonal signal indicating the transmitting procedure of video information with the modulator and VSB filter. CONSTITUTION:The tonal signal of desired frequency is output from the carrier generating circuit 14 with the control signal from the control circuit 40. The tonal signal is input to the MODEM34 via the contact 31a of the switch 31 and modulates the DC signal of video signal, allowing the fundamental wave component of the output signal of the MODEM34 to match with the frequency of tonal signal. The high frequency components of this tonal signal are rejected at the VSB filter 35 and the speaker 37 is energized via the amplifier 36 when the switch 33 is ON. In this case, to avoid unnatural sound through the output level of high frequency lowered at the VSB filter, the level of each frequency of tonal signal at the output of the filter 35 is kept constant by combining the output signals 27a, 27b of the control circuit 27 at the amplifying and control cricuit 28. Further, the tonal signal is converted into ease of hearing through the rejection of high frequency components at the filter 35. |
