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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.
R175
R176
R174
Mic
C80
Q19
C76 R177
Mic Amp.
(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.
D15
6 V
1
Circuit Diagram
ALC Amp.
C38
+
9
R178
ALC
10
–
11
C34
R26
C33
R27
RF
Modulation Circuit
Circuit Diagram
D16
1
C34
R149
Timing Chart
VC Microcomputer Voltage
Microcomputer Clock
1 Voltage
2 Voltage (Reset)
3 Power Down
(IC1)
13
LIMIT
15
18
R22
LPF
24
R151
2
7
6
IC5
3
|182 |
CPU
23
46 Pin
Mic Mute
C27
20
COMP
R18
22
Mixer
R19
21
25
2
CPU
5
9
3
Reset
CPU
Power
25
Down
R20
C26
C25
CPU
~
38
41
TX Data
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