| 摘要 |
<p>PURPOSE:To prevent sound noise from being generated when a lamp is activated even in the case of using metal vapor discharge lamp for the lamp by muting sounds for a prescribed period after starting the power supply of a lighting circuit. CONSTITUTION:An inputted sound signal is processed at a sound signal processing circuit 8, afterwards, inputted to a mute circuit 12 and muted by a changeover switch 13 for the period of delay time DELTAt2 to be determined by a delay circuit 14 from time T1. Therefore, although the sound signal is inputted, any sound is not generated from a loudspeaker 9. At time T3 after the lapse of DELTAt2 from time t1, the sound signal processed at the sound signal processing circuit 8 bypasses the mute circuit 12 by the changeover switch 13 and drives the loudspeaker 9. At such a time, by prolonging the delay time DELTAt2 rather than high voltage pulse generating period DELTAt1, the uncomfortable tones are prevented from being generated by loading the noise onto the sound signals with interruption from the lighting circuit.</p> |
