8
KX-TS820MXB/KX-TS820MXW
4.2.
Circuit Operation
4.2.1.
Power supply circuit
The set is powered from the line, 48V/24V.
•
Off hook
LINE
→
Q101
→
Q107
→
R119
→
D106
→
D201
→
D203
→
Vdd (pin7 of IC1)
•
On hook
LINE
→
R101
→
R102
→
D101
→
SW1(pin 5-6)
→
R13
→
D102
→
D6
→
Vdd (pin7 of IC1)
4.2.2.
Bell Ringer Circuit
When the bell signal is input from LINE to T/R (when the telephone rings), the signal is detected and output by micon to the
buzzer via the following path :
•
Bell Detection circuit
T / R
→
C1
→
D2
→
R2
→
Q1
→
RINGDET (pin 27 of IC1)
•
Bell Output circuit
Pin 15 of IC1
→
Q3
→
Q2
→
R9
→
SW2/3
→
Buzzer
4.2.3.
Telephone Line Interface
4.2.3.1.
Circuit operation
•
On hook
Q101 is OFF, on-hook condition where DC loop is disconnected and voice signal flow is cut.
•
Off hook
During Off-Hook, pin 4_6 of SW1. Q101 is ON, providing an off-hook condition (active DC current flow through the circuit) and
the following is the signal flow :
T
→
POS101
→
L101
→
D101(+)
→
Q101
→
Q107
→
R119
→
D106
→
D101(-)
→
L102
→
R
•
Receiving signal flows:
LINE
→
Q101
→
C114
→
C301
→
R301
→
Q301
→
C305
→
R307
→
C306
→
Q306
→
C310
→
R315
→
Q308
→
C315
→
R318
→
SP (handset)
•
Transmission signal flows:
MIC (handset)
→
C402
→
R402
→
R405
→
C405
→
Q401
→
R409
→
C410
→
Q107
→
Q101
→
LINE
•
Pulse Dial
A pulse signal switches repeatedly between high and low logic is output from IC1 (pin 11), on and off the line loop, generating the
pulse dial signal.
