17
KX-TGH260/KX-TGH262/KX-TGH263/KX-TGH264/KX-TGHA20/KX-TGA20
4.5.8.
Parallel Connection Detect Circuit/Auto Disconnect Circuit
Function:
In order to disable call waiting and stutter tone functions when using telephones connected in parallel, it is necessary to have a
circuit that judges whether a telephone connected in parallel is in use or not. This circuit determines whether the telephone
connected in parallel is on hook or off hook by detecting changes in the T/R voltage.
Circuit Operation:
Parallel connection detection when on hook:
When on hook, the voltage is monitored at pin 32 of IC501. There is no parallel connection if the voltage is
0.54 V or higher, while a parallel connection is deemed to exist if the voltage is lower.
Parallel connection detection when off hook:
When off hook, the voltage is monitored at pin 17 of IC501; the presence/absence of a parallel connection is determined by
detecting the voltage changes.
If the Auto disconnect function is ON and statuses are Hold, receiving ICM, OGM transmitting, BBIC disconnects the line after
detecting parallel connection is off hook.
C174
C171
R166
R178
RX
Pin25 of IC501
TX
Pin27 of IC501
R160
+
C161
C167
R165
R162
C173
R151
R164
C184
Q161
E
B
C
R163
R1
17
C1
15
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
R142
SA101
HOOK
Pin19 of IC501
R168
PARADET
Pin17 of IC501
ADC1
Pin33 of IC501
ADC0
Pin32 of IC501
R1
18
C1
16
R115
R116