External Microphone - Nokia RM-42 Service Manual

RM-42
System Module Nokia Customer Care
Figure 111 Audio block diagram
Internal microphone
Internal microphone is used for HandPortable (HP) and Internal HandsFree (IHF) call modes.
An analogue electret microphone is connected to Retu ASIC's Mic1P and Mic1N inputs via asymmetric electrical
connection.
The microphone is biased by Retu ASIC MicB1 bias voltage output.
Figure 112 Internal microphone circuitry

External microphone

TM
Galvanic accessories are connected to the system connector (Pop-Port ).
Accessory audio mode is automatically enabled/disabled during connection/disconnection of dedicated phone
accessories.
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