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182
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KX-F910BX
(6) Sending Signal
The received voice signal from the microphone is amplified in the microphone amplifier of Q19 and input to the ALC
amplifier of IC1. The ALC circuit prevents the received voice signal from being distorted when a large volume signal
is input from the microphone. If an input signal level becomes beyond the previously set one, the circuit reduces the
Amp. gain in order not to fluctuate the output level by strong input. The LIMIT circuit clips strong signals that are
leaked from ALC filtering. The transmitted voice signal output from pin 15 is input to the compressor from pin 18 and
amplified. Then, it flows through the MUTE circuit and output to pin 20. This circuit controls the CPU when the sig-
nal is Low during calling and High during muting mode. The transmitted voice signal through the MUTE circuit is in-
put to the HPF of pins 21 and 22, and sent to the Mixer circuit in IC1.
The Mixer circuit mixes the TX data from the CPU with the transmitted voice signal (however, Mic. Mute mode is ac-
tivated during TX data transmission). Finally, the Mixer output flows through the LPF of 4 kHz cut-off frequency and
it is output from pin 24, then sent to the RF modulator.
Circuit Diagram
~
Mic
R174
C76 R177
Mic Amp.
R175
C38
C80
Q19
R176
ALC Amp.
9
10
+
–
R178
C34
R27
11
RF
Modulation Circuit
ALC
13
LIMIT
15
18
COMP
(IC1)
LPF
Mixer
24
23
20
22
21
25
38
41
CPU
TX Data
CPU
46 Pin
Mic Mute
R22
R26
C33
C27
R20
C26
C25
R18
R19
D15
6 V
D16
R149
C34
IC5
R151
2
5
6
7
1
1
3
25
CPU
Power
Down
9
CPU
Reset
2
3
(7) Reset Circuit
After the power supply to work is put, the voltage at point 1 is raised to the same level of the microcomputer.
However, since D16 is 3.3 V Zener, the voltage of RESET stays Low until D16 is turned ON. When D16 is ON,
the Power Down becomes High and the output of the RESET becomes Low for about 20 ms, then the RESET
is activated.
Circuit Diagram
Timing Chart
VC Microcomputer Voltage
Microcomputer Clock
1 Voltage
2 Voltage (Reset)
3 Power Down
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