Icom IC-H12 Maintenance Manual page 9

4
• 3 2 L ED I N D I CA TO R C I R CUIT
- -
is L E D
ot be lit.
e power supply voltage is divided by R148 and R149, and applied to the base of 0121. The emitter
o 0121
121 is turned
E is
4
3 3 DIO D E MA T R I X BOA R D
- -
e se
be progra med into the board.
-
-5
•
a
ece·.e
:.:ge
06
•
is lit in the transmit mode, but when the power supply voltage becomes less than 5. 5V, it will
is connected to the regulated 5V source. When the power supply voltage is more than 5. 5V,
O F F, 0122 is turned O N and T+5V is applied to the L E D through 0122 and R150, and
Ii .
corporates a diode matrix
·
ed to B C D codes by diodes programmed into the board, then fed to IC201 to determine an
equency (channel) .
s nc ion is provided
a
· s
a plied o he base
� ects X204. and he transmitting frequency
is provided by inserting a diode into the receive only line. At this time, a
s ap
o t e base of 0107 on the MAI N board through R404, and it turns 0107 ON and
·
FF.
e se does not turn to the transmit mode, even if the PTT switch is depressed .
board to determine its operation frequencies, and twelve channels
by inserting a diode into the duplex line on the board. At this
of 0402, and turns 0402 and 0401 ON. Thus T+ 5V is applied to
shifts specified offset frequency.
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