Panasonic KX-TGF340B - Telephone Line Interface

17
KX-TGF340/KX-TGF342/KX-TGF343/KX-TGF344/KX-TGF345/KX-TGF372/KX-TGF373/KX-TGF374/KX-TGF375/KX-TG585/KX-TGFA30
4.6.6. Telephone Line Interface
Telephone Line Interface Circuit:
Function
• Bell signal detection
• ON/OFF hook and pulse dial circuit
• Side tone circuit
Bell (RINGING) signal detection and OFF HOOK circuit:
In the idle mode, Q141 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:
L1T  C105  R105  R110  R11 1 R112  BBIC pin18(RINGING)
When the CPU (BBIC) detects a ring signal, Q141 turns on, thus providing an off-hook condition (active DC current flow through
the circuit). Following signal flow is the DC current flow.
T  D101  Q141  Q161  R163  D101  P101  R
ON HOOK Circuit:
Q141 is open, Q141 is connected as to cut the DC loop current and to cut the voice signal. The unit is consequently in an on-
hook condition.
Pulse Dial Circuit:
Pin 19 of BBIC turns Q141 ON/OFF to make the pulse dialing.
Side Tone Circuit:
Basically this circuit prevents the TX signal from feeding back to RX signal. As for this unit, TX signal feed back from Q161 is
canceled by the canceller circuit of BBIC.
C172
C171
R166
R178
RX
Pin25 of IC501
TX
Pin27 of IC501
R160
+
C164 C161
C167
R165
R162
TP9
C173
C165
R161
R164
C184
C107 C103
C113
C163
Q151
E
B
C
R151
R163
C168
C186
C111
R110
C110
R112
C181
R109
C109
Q141
Q142
C101
P101
L1T
L1R
D101
C102
1
2
3
+
~~
_
4
R145
C142
C152
R152
A
K
D142
R141
B
E C
E
B
C
R144
R131
R133
C132
R142
(3216)
SA101
TP10
R111
RA101
RA101
C108
R103
R105 C105
C106
C104
R106
R101
R102R104
HOOK
Pin19 of IC501
CIDOUT
Pin24 of IC501
LSRn
Pin28 of IC501
RINGING
Pin18 of IC501
CIDINn
Pin23 of IC501
CIDINp
Pin21 of IC501