| 摘要 |
PURPOSE:To enable loundspeaking broadcast with a suitable sound volume for a broadcast district without the operation to a loudspeaker receiver at a base station side. CONSTITUTION:After noise through a microphone 1 is amplified at an amplifier 2, correction according to the frequency characteristics of ears is made at a frequency correction circuit 3, and the noise is detected at a detection circuit 4 and stored in sampling hold circuits 5-7. The sampling of noise is made for a minute time t1 with a timer circuit 8 and stored for a specified time t2. This operation is repetitively made at a time where no broadcast signal is present. When a broadcast signal from a base station is received at an antenna 18, amplified at a high frequency reception section 16 and detected at a detection circuit 17, the noise sampling is stopped, the output of sampling hold circuits 5-7 is stored in a sampling hold circuit 11 through an average circuit 9 and log circuit 10, to operate a voltage control attenuator 13 for the adjustment of sound volume of broadcast. |
