Nokia RH-64 Service Manual page 172

RH-64
Nokia Customer Care System module
Figure 146 Audio block diagram
UEMCLite supports three microphone inputs and two earphone outputs. The microphone signals from different
sources are connected to separate inputs at the UEMCLite ASIC. The inputs and outputs are all differential.
Three inputs (MIC1, MIC2, MIC3) and two outputs (EAR, HF/HFCM) are used. MIC1P/MIC1N input is used for the
internal microphone, using single-ended biasing circuitry. EARP/EARN output from UEMCLite is used for hand-
portable mode.
Uplink external audio (headset as well as car kit) is connected to MIC2P/MIC2N, while downlink audio is provided
via the HF/HFCM output from UEMCLite. The car kit only can be used with external microphone connected.
MIC3 (positive input) connects to single ended outputs from the FM radio. The other input MIC3N is AC-coupled
to GND.
The audio control is taken care of by UEMCLite, which contains the MCU and audio codec. Input and output
selection, and gain control is performed inside UEMCLite. DTMF-tones and other audio tones are generated and
encoded by UPP and transmitted to UEMCLite for decoding.
An external amplifier (D-class) is connected to provide sufficient power for an 8 W load. The inputs are wired
to the headset connections HF and HFCM from UEMCLite.
EARP/N output is used for hand-portable speech, connected with PA output through switches.
Under normal conditions HF and HFCM is used for downlink audio to the headset/car kit. During headset/car kit
usage the audio amplifier is disabled by means of the shutdown pin. Keeping the shutdown pin "low" also
during sleep, secures a minimum amount of standby current to be consumed.
SMD vibra has a diameter is about 4.0-mm. Vibra is driven by PWM signal, generating vibration by rotating an
un-balanced mass (counter weight) with radius of R=2.3-mm. The vibration signal is used as a silent alert call
and also as a noticeable shock in gaming.
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