User Guide

CCS Technical Documentation 2 - System Module
RH-26
Issue 1 02/04 ©Nokia Corporation Page 35
Internal audio
IHF speaker & audio amplifier
Integrated handsfree speaker, 16mm MALT, is used to generate alerting and warning
tones in RH-26. IHF speaker is driven by the audio amplifier (LM4890 & NCP2890) exter-
nal to the UEMK. The speaker capsule is mounted in the antenna assembly. Spring con-
tacts are used to connect the IHF Speaker contacts to the main PWB.
Figure 16: Block diagram of IHF speaker and amplifier
Internal microphone
The internal microphone is connected to the UEMK microphone input. The microphone
input is symmetric and microphone bias is provided by the UEMK. The microphone input
on the UEMK is ESD protected. Microphone capsule is mounted in the UI Module. Spring
contacts are used to connect the microphone contacts to the main PWB.
Figure 17: Internal microphone connection
Internal speaker
The internal earpiece is a dynamic earpiece with impedance of 32 ohms. The earpiece
must be low impedance, since the sound pressure is generated by using current and not
voltage as the supply voltage is restricted to 2.7V. The earpiece is driven directly by the
UEMK and the earpiece driver in the UEMK is a bridge amplifier. In RH-26, 8mm PICO
type earpiece is used.
IHF speaker
Mono
audio
A
mplifier
UEM
EARN
UPP
VBAT
GenIO(13)
_
SD
EARP
XEAR
33nF
UEM
MIC1B
MIC1P
2k2
33nF
MIC1N
2k2
22pF
600
Ω
@100MHz
2k2
100nF
1nF