Panasonic KX-TS880MXB, Руководство по обслуживанию

Страница: 8 / 44

8
KX-TS880MXB/KX-TS880MXW
4.2. Circuit Operation
4.2.1. Bell Detector Circuit
When the bell signal is input from LINE to T/R (when the telephone rings), the signal is output at the speaker via the following
path :
T/R
→
R1/C1
→
D1/LED1 (small PCB)
→
D3/D6
→
IC1 (pin8)
→
IC1 (pin5)
→
PC1
→
C5
→
SW2 (R7/R8)
→
T1
→
Speaker
4.2.2. Telephone Line Interface
4.2.2.1. 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 1_3 of SW101 and 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
→
R180
→
Q107
→
R119
→
D103
→
D101(-)
→
L102
→
R
• Receiving signal flows:
LINE
→
Q101
→
R180
→
C109
→
C401
→
R401
→
L412
→
L401
→
Q401
→
C404
→
R405
→
R417
→
L405
→
C405
→
L406
→
Q402
→
C408
→
R413
→
L409
→
Q403
→
C410
→
VR401
→
SP (handset)
• Transmission signal flows:
MIC (handset)
→
C422
→
VR402
→
R423
→
C425
→
L421
→
R430
→
Q422
→
R429
→
C429
→
L107
→
Q107
→
Q101
→
R180
→
LINE
• Pulse Dial
A pulse signal switches repeatedly between high and low logic is output from IC801 (pin 73), on and off the line loop, generating
the pulse dial signal.