| Function test for internal microphone -R74- |
| An internal microphone -R74- is installed on vehicles with the BOSE Sound system to measure interior noise levels (AudioPilot). It is connected directly to the amplifier -R12-. When noise increases in the interior, the amplifier -R12- (Audiopilot) automatically adjusts the volume according to a preset pattern. |
| When the radio -R- is switched on, the amplifier -R12- checks the voltage supply level of the internal microphone -R74-. If the result is OK, there is no reaction. |
| If, however, the microphone -R74- is not installed, three short tones are emitted three times. |
| In the case of a short circuit, three short tones are emitted. |
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| Switch on the radio -R- and tune in to a station (preferably pop music). |
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| Set the volume level to approx. “20”. |
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| Tap lightly on the internal microphone -R74- (front interior light -W1-) for a while. |
| You should hear the volume of the radio -R- increase. The process occurs slowly. |
| The volume of the radio -R- should decrease audibly. |
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