Service manual

There are three audio outputs provided by GCAP-II, Taichi used two for its
application. One is for its earpiece speaker and another one is for external
speaker audio output. For driving those audio output signals, one amplifier is
connected with each of the three outputs. For those amplifiers: A1 is for transceiver
earpiece speaker amplifier, A2 is for Alert amplifier and A4 is for External audio
output amplifier.
A1 – Earpiece Speaker Amplifier, is powered by V2 and is driven through a
multiplexer by the audio CODEC output.
A2 – Alert amplifier. Is powered by ALRT_VCC and is driven through a
multiplexer by the audio CODEC output.
A4 – External Audio Output Amplifier, is powered by V2 and is driven
through a multiplexer by the audio CODEC output.
Above is a block diagram of the audio output section. Any one of three
outputs can be selected. These outputs connect to the earpiece speaker
amplifier, A1, the alert amplifier, A2, and the external audio out amplifier, A4.
All outputs use the same converter so only one output is active at a time. The
gain of the output can be selected in 5dB steps from -35dB to +0dB. This gain
block is an analog system.
The Audio Output bits are programmed via SPI and they control the
configuration of the output section. These bits select the gain, enable or
disable the audio output, select or deselect dithering, and select or deselect
the high pass output filter.
2. Audio Input
There are three audio inputs provided by GCAP-II, Taichi used two for its
application also. One is for its transceiver microphone and another one is for its
external microphone input. For driving those audio input signals, one amplifier is
connected with each of the three inputs. For those amplifiers: A3 is for transceiver
microphone amplifier, A5 is for the AUX microphone Amplifier. No audio amplifier
was connected with external audio input. Amplifiers of A3 and A5 are powered by V2
and drive the audio CODEC input. Taichi phone use the without amplification
external microphone input for the headset microphone.
Below is the block diagram of the audio input section. Any one of three equivalent