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Power Supply Circuit
When the POWER switch on the display unit is pressed,
the power port on the display unit which is connected to
CPU port 18 (POWER), goes low, then CPU port 93 (SBC)
goes high, Q34 turns on, SB SW (Q42) turns on and power
(SB) is supplied to the radio.
This circuit has an overvoltage protection circuit. If a DC
voltage of 18 V or higher is applied to the power cable, D39
turns on and a voltage is applied to the base of Q38. This
voltage turns Q38 on and turns Q34 and SB off.
POWER
CIRCUIT DESCRIPTION / 电路说明
B
Q16
IGN
SW
SBC
IC6
5M
CPU
POWER
RESET
SW
Fig. 16 Power supply circuit / 图16 电源电路
电源电路
当按下前面板中的POWER开关时，显示板上与CPU端口18
(POWER) 相连接的电源端口为低电平，然后CPU端口93 (SBC)
为高电平，Q34导通，SB SW (Q42) 导通并向通信机供电 (SB)。
此电路具有过载电压保护电路。如果18V或更高的电压被提
供给电源电缆，则D39导通并向Q38的基极提供电压。此电压使
Q38导通，使Q34和SB断开。
Q42
SW
Q34
SW
D39
Q38
SW
5M
IC17
AVR
IC15
RESET
IC18
INT
TK-7108
B
23
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