Nokia 8208 Service Manual page 153

RM-384
System Module and User Interface
Internal microphone
MIC1_P & MIC1_N inputs of 8208 schematic are used for the mobile terminal's internal microphone. MIC2_P &
MIC2_N input are used for headsets.
Every microphone input can have either a differential or single-ended AC connection to the MSM6800 circuit.
The internal microphone is differential signals. External headset microphone is single-ended.
MIC_AMP_BIAS (2.8V) regulated voltage from PM is used for microphone.
Figure 74 Internal microphone circuitry
Internal Receiver (earpiece)
EAR_P & EAR_N of MSM6800 output pins outputs are used for the mobile terminal's internal earpiece (receiver).
The earpiece (receiver) and external louder speaker are both differential signals that come from separate
outputs at the MSM6800 are connected to different driver.
The output power for the differential earpiece output is typically 108 dB for +/- 3 dB, Impedance is 32 ohm in
1kHz.
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