Panasonic KX-TC1085BXB, Service Manual

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Q101(Q201)* is open, Q101(Q201)* is connected as to cut the DC loop current and to cut the
voice signal. The unit is consequently in an on-hook condition.
Bell detect
In the idle mode, Q101(Q201)* is open to cut the DC loop current and decrease the ring load.
When ring voltage appears at the Tip (T) and Ring (R) leads (when the telephone rings),the AC
ring voltage is transferred as follows:
T POS101 C118 R123 PC102 IC701 Pin 30: LINE1(T POS201 C215 R214
PC202 IC701 Pin 32:LINE2)*
When the CPU detects a ring signal, Q101(Q201)* turn on,thus providing an off-hook condition
(active DC current flow through the circuit) and the following signal flow is for the DC loop
current.
T POS101 D101 Q101 Q102 R110 D105 D101 R:LINE1
T POS201 D201 Q201 Q202 R212 D205 Q207 D204 D201 R:LINE2
The receiving signal flows:
POS101(POS201)* Q101(Q201)* C108(C207)* C110(C209)* R114(R211)* Q103(Q203)*
C115(C220)* R137(R231)* Q104(Q205)* PC103.
The transmission signal flows:
Line1: IC402 Pin 11 VR101 R131 C124 Q106 PC104 C111 R109 Q101
POS101
Line2: IC402 Pin 12 C210 C212 R209 Q201 POS201
NOTE:
( )*: In case of Line 2
16.11. Initializing Circuit
16.11.1. Function:
This circuit is used for to initialize the microcomputer when it incorporates an AC adaptor.
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