External Audio Connector - Nokia RM-392 Service Manual

RM-392; RM-393
System Module
Figure 109 Audio block diagram
Liteplus supports three microphone inputs and two outputs. The inputs can be used for internal, headset or
handsfree microphones. The microphone signals from different sources are connected to separate inputs at
the Liteplus ASIC. The inputs and outputs are all differential.
Three inputs (MIC1, MIC2) and two outputs (EAR, HF) are used in the phone.
MIC1P/MIC1N inputs are used for the internal microphone, using single-ended biasing circuitry. EARP/EARN
outputs from Liteplus are used for hand-portable mode.
Uplink external audio (headset as well as carkit) is connected to MIC2P/MIC2N, while downlink audio is
provided via the HF outputs from Liteplus. A special situation exists since the carkit can be used with two
different microphones: either the phone's internal microphone (MIC1-inputs) or an external microphone that
connects to the carkit. In these cases Liteplus is capable of switching between MIC1 and MIC2.
The audio control is taken care of by Liteplus, which contains the MCU and audio codec. UPP contains DSP
blocks, and handling and processing of the audio signals.
Input and output selection, and gain control is performed inside Liteplus. DTMF-tones and other audio tones
are generated and encoded by UPP and transmitted to Liteplus for decoding.

External audio connector

The system connector, containing a 4-pole Jack plug, gains the access to the external audio interface. The
Jack plug, which is integrated in the system connector, contains a mechanical switch, which is used to detect
the connection of the accessories. The configuration for the 4-pole Jack-plug is shown in the following figure.
Issue 1 COMPANY CONFIDENTIAL Page 6 –9
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