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 108 Internal microphone circuitry
External microphone
Galvanic accessories are connected to the system connector (Pop-Port
TM
).
Accessory audio mode is automatically enabled/disabled during connection/disconnection of dedicated phone
accessories.
External microphone circuitry is biased by Retu ASIC MicB2 bias voltage output. The circuitry provides a
symmetrical connection for the microphone from the Pop-Port
TM
connections, XMICN and XMICP, to Retu ASIC
inputs, Mic2P and Mic2N.
Figure 109 External microphone circuitry (Pop-Port connects to the right side)
Internal earpiece
Internal earpiece is used for the HandPortable (HP) call mode. A dynamic 8mm earpiece capsule is connected
to Retu ASIC’s differential output EarP and EarN.
RM-57/58
System Module
Nokia Customer Care
Issue 1
Company Confidential
Page 9–25
Copyright ©2005 Nokia. All Rights Reserved.
Summary of Contents for RM-57
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