Kenwood TM-V708A Service Manual page 11

6-2. Speaker Switching Circuit
There are two speaker jacks, J801 and J802. The AF
signals can be output in various combinations matching the
internal speakers.
When no external speaker is connected to J801, Pins 5 of
the multiplexer (IC807, IC808) go low, the AF signals AO 0
and AO 1 are added and input to the power amp (IC806).
When an external speaker is connected to J801, Pins 5 of
the multiplexer (IC18) go high and AO 0 and AO 1 are input
separately to the power amp.
CROSS POINT SW
IC702
RAV
RAU
6-3. Microphone Key Input
The microphone UP/DOWN and function keys are
connected to the microprocessor analog input. The voltage
when a key is ON operates the corresponding function. Also,
the key input interrupt circuit is for switching the power ON/
OFF with the microphone. When the DOWN, MR, and PF
MICRO
PROCESSOR
IC604
MIC PTT
MIC UP
MIC DW
INT3
CIRCUIT DESCRIPTION
ELECTRONIC
VOLUME
IC804
R857
AO 1
1
7
R858
AO 0
1
IC807
CPU
IC604
Fig. 14 Speaker switching circuit
M 5C
5C
R806
IC800
KEY INPUT INTERRUPT CIRCUIT
Fig. 15 Microphone key input circuit
The AF signal output combinations are as in the speaker
combination table on the below.
Internal speakers only
1 external speaker (J802)
1 external speaker (J801)
2 external speaker
Table5 Speaker combination table
POWER AMP
MUTE
R874
13
Q804
IC 808
7
5
MUTE
R875
1
6
Q805
5
D803
keys are pressed, an interrupt is generated and the
microprocessor is awoken from stop mode. However, with
the TM-V708A, the power ON/OFF switch function can be
registered to the PF key on the microphone.
R804
R803
R805
TM-V708A
AO 1 AO 0
Internal speaker
external speaker
Internal speaker external speaker
external speaker external speaker
IC806
J802
8
CN800
6
J801
MIC
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