Service Manual

17
(control signal of SAVE). When the SAVE signal of MCU is of high level, Q610 becomes conductive
and provides a 5V voltage (V_SAVE) for the operating circuit. PLL and the receiving circuit operate.
When the SAVE signal is a pulse signal, the radio enter the battery save mode. When transmitting,
TXC, control signal of CPU, is of high level. Q611 becomes conductive and provide a 5V voltage for
the transmitting circuit and the transmitting circuit operates.
Power supplies of the Tx section and Rx section both have symmetrical regulation measures.
When the load change changes the output voltage/current, the regulator closed-loop feedback
circuit operates, regulating the output voltage at 5V.
VOX Realization
The block diagram is shown below:
Q202
2SA1832
1
2 3
Q201
2SK1824
2
31
J4
MICJACK
2431
VCC_5V
R251
1M
MIC_EN
EXPTT
C260
220P
RXD
mic
X1
-
2
+
1
R201
2.2K
C201
470P
C200
4.7u/10V
R203
4.7K
VCC_5V
R200
470
C213
1U
C212
0.1U
R205
47K
C202
0.1U
L200 1UH
R202 100
TP200
R208
100K
R207
56K
R206 1K
R204 470
C274
0.01U
Figure 11
After the function key VOX is held down, the radio enters the VOX status. The VOX function can
only be enabled when MCU detect that MIC enabling signal (MIC_EN) and external VOX enabling
signal (EXT-PTT) switch from low level to high level almost at the same time (within hundreds of
milliseconds). Otherwise, it is detected as the earpiece without VOX and the VOX function is off.