| 摘要 |
When microphones are used in a noise-filled environment, e.g. for announcements in vehicles in local public transport, the driver must move his mouth near to the microphone when speaking and simultaneously actuate a switch by hand which connects the microphone to the transmission device. To eliminate the additional manual burden, which distracts the speaker from other tasks, a proximity sensor is fitted to the microphone which continuously measures the distance of the speaker's head. A switch is actuated with its output signal if the speaker's head comes closer to the microphone than a minimum distance. This switch then connects the microphone to the transmission device, e.g. to the amplifier and connected loudspeaker. Known ultrasound sensors, optical sensors or electric-field sensors can be used as proximity sensors. To prevent short-time activation of the microphone through accidental movement of the head in the vicinity of the minimum distance, a hysteresis range is provided for the switch activation.
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