| 摘要 |
PURPOSE:To reduce the installation cost of a slave station and to transmit surely the message from a master station, by using a speaker of the slave station as a sound collecting microphone when no message is transmitted from the master station. CONSTITUTION:The message from the master station received on an antenna 1 of a slave station noise detection broadcasting system at a receiver 2 and the noise level around the slave station detected at a noise level detector 4 is added to a sound volume adjusting device 5. The speaker of this broadcasting system is constituted as a speaker 8 in common use of sound collecting microphone and the speaker 8 is changed over into the broadcasting system and the sound collecting system with a relay 7. The relay 7 is operated with a start signal from the master station, and when no message is transmitted from the master station, the speaker 8 detects the noise level around the slave station as the sound collecting microphone. When the message is transmitted, the device 5 is locked to the noise level just before the message receiving, the speaker 8 is changed over to the broadcasting system, allowing to reduce the installation cost of the slave station and to transmit surely the message. |
