Vox Realization - HYT TC-610 Service Manual

VOX Realization

The diagram is shown below:
VCC_5V
C274
R251
1M 0.01U
L200
After the function key VOX is held down, the radio enters the VOX mode. The VOX function can only be
enabled when MCU detects that MIC enable signal (MIC_EN) and external VOX enable 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.
1) When the earpiece with VOX is inserted into the accessory jack, Q201 is off. MIC_EN switches from
low level to high level and Q202 completes the circuit with R204 and the external earpiece
simultaneously. Q202 is on and EXT-PTT switches from low level to high level, which is detected by
MCU as the insert of an earpiece with VOX. The VOX function is enabled. When the VOX detect
level (5 levels available) meets the preset requirements, the radio transmits and the audio signal
goes to baseband processor AN29160 through the process path.
2) If an earpiece without VOX (earpiece with PTT) is inserted, Q201 is off. MIC_EN switches from low
level to high level, but Q202 can not complete the circuit and keeps the cut-off status. EXT-PTT is of
low level. MCU detects as the earpiece without VOX and the radio returns to normal mode. Press
the PTT key on the earpiece to transmit.
R206 1K
C212
R205
0.1U
47K
C213
1U
Q201
2SK1824
2
R203
4.7K
1UH
Q202
2SA1832
2 3
R207
56K
R204 470
C260
R202 100
220P
TP200
C202
0.1U
C201 R201
470P 2.2K
C200 R200
4.7u/10V 470
Figure 11
19
TC-610/620 Service Manual
R208
100K
J4
MICJACK
X1
2
-
1 mic
+
VCC_5V
EXPTT
MIC_EN
RXD