Panasonic KX-F900 Service Manual page 174

I ..... KX-F900
(3) Line Receiving Signal
The signal supplied from the line is input from pin 6 of CN501 through the analog board, and ti is output from
pin 10 of the RF unit via IC502 pins 21,20, 19, 17, 16, 13, 11 and 10 in this order.
R553 R622
L507 C571_'-_ C572
(6pin) VR503 _'R554 C518
Circuit Diagram
MPU
TX MUTE
6)
_ 0 ' To
I IC502 Compander
(4) RX Data Circuit/Hard Mute Circuit
The AF signal output from the RF unit is filtered and amplified by a filter amplifier with a 500 Hz cutoff
connected to pins 1 through 4 of IC503. The resulting demodulated data waveform is then input to RX
DATA pin 6 of the MPU.
If there is data from the portable handset during talk operation, the portable handset data is as shown below
to prevent the data from leaking onto the line. Hardware muting is applied as the leading edge of the data
as soon as the data arrives. After this, muting is applied by the MPU.
Timing Chart
_J_Bed --I
eiected at peak level
HARD MUTE__[
I
RX MUTE
Circuit Diagram
C550 C552
R FAUpIT _R616 C551_--_ R618
C5421 _ i --:'1 _ I _ MPU l-
CCN502(3pin, i R60_9 __ RXDATA /
I .61o sc o3 o o31
I
C547 Ix,._ D507 t:1607 t_
] R608R611_'I_I'--lC574 R612 Q504 +('_'_ _ +
C541 _':
E
MPU D508
RX MUTE
(5) ID Code Setting
When the portable handset is placed on the cordless base unit, the charge detector operates and ID data is
output from pin 44 of the MPU. After passing through data amplifier Q506 and the charge terminal, the data
is sent to the portable handset.
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