For this mode a microphone has to be connected to at least one of the M302 / M312 inputs.
![1](drex_bullet_1.png) Signal input
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Selects the physical input and the gain of the USB device. The connected sensor has to be a microphone (sound pressure sensor). Otherwise acoustic measurement will be disabled.
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![2](drex_bullet_2.png) Characteristic
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Selects the weighting filter and automatically sets the time constant
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