9
KX-TS620BX1
4.2.3.
Telephone Line Interface
Function:
• Bell Signal Detection
• Caller ID Detection
• ON/OFF hook Circuit
• Audio Circuit
4.2.3.1.
Bell Detection Circuit
When the bell signal is input from LINE to T/R (when the telephone rings), BBIC detects bell signal via following path:
T -> D3 -> IC1(1) -> IC1(8) -> C4 -> R6 -> PC1(1) -> PC1(4) -> IC901(63)
R -> R1 -> LED804 -> D4 -> IC1(1) -> IC1(8) -> C4 -> R6 -> PC1(1) -> PC1(4) -> IC901(63)
After bell signal detected at IC901(63), the bell ringing signal is output at the speaker via the following path:
4.2.3.2.
Caller ID Detection Circuit
Normally, FSK caller ID data is followed after the 1st bell signal.
When the bell signal is detected by BBIC, Caller ID signal is sent through the circuit via
following path:
T -> C501 -> R503 -> R905 -> IC901(107)
R -> C502 -> R504 -> R908 -> IC901(112)
4.2.3.3.
On/Off Hook Circuit
In standby mode, SW101 is open and Q104 is OFF. Consequently Q103 is open and cut the DC loop current and voice signal.
This is an
on-hook condition
.
When handset is picked up or SP-Phone key is pressed, Q104 turns on and then Q103 turns on, thus providing an
off-hook
condition
. A DC loop is made and current flows through the circuit via following path:
T -> D7 -> Q103 -> Q108 -> R124 -> D106 -> D10 -> R
Pulse signal is generated by repeated switches between high (3.2V) and low (0V) logic output from IC901(79), switching the line
loop on and off.
4.2.3.4.
Handset Circuit
* Refer to
4.2.3.5.
Speakerphone Circuit
* Refer to
IC901(110) -> C930 -> R925 -> IC904(4) IC904(
8
) -> C925 ->
S
P(+)
IC904(5) ->
S
P(-)
