Samsung SCH-570, Service Manual

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5-1-4 Audio Part
TX AUDIO PATH
The voice signal output from microphone is
filtered and amplified by the internal OP-AMP
and is converted to PCM data by the CODEC
(U117). The signal is then applied to the MSM
(U101)’s internal vocoder.
RX AUDIO PATH
The PCM data from the MSM’s converted to audio
signal by ADC of CODEC (U117), is then
amplified by the speaker amplifer (U111) to be
sent to the speaker unit.
TX WBD, ST,SAT
These signals are generated from MSM. The
modulation level of TX WBD and ST is 8
kHz/dev, and SAT is
2 kHz/dev.
BUZZER DRIVING CIRCUITRY
Buzzer generates alert tone when the buzzer
receives the timer signal from the MSM, it
generates alert tone. The buzzer level is adjusted
by the alert signal’s period generated from the
MSM timer.
KEY TONE GENERATION
Ringer signal (pin49) out from MSM (U101) is
passed through 2 serial LPF consisting of R141,
C146, R145, and C142 amplified at the speaker
amp (U111), and comes out to speaker.
5-3