Panasonic KX-TC2101BXB, Service Manual

Page: 35 / 63

14.4. Charge Circuit
Circuit Operation:
When charging the handset on the base unit, the charge current is as follows;
DC12V
→
L101
→
D102
→
L103
→
CH+(Base)
→
+CONTACT J601(Handset)
→
L602
→
D602
→
CN1-1
→
Battery
→
CN1-2
→
-CONTACT J602(Handset)
→
CH-(Base)
→
L104
→
Q102
→
R104
In this way, the CPU on both units detects the fact that the battery is charged.
The charge current is controlled by switching Q103 of Base Unit. The battery is charged in normal mode for 9 hours and then
in trickle mode.
14.5. Telephone Line Interface
Function:
•
Bell signal detection
•
ON/OFF hook and pulse dial circuit
•
Side tone circuit
Bell signal detection and OFF HOOK circuit:
In the idle mode, Q301 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:
•
JK1 TIP
→
P0301
→
L301
→
R334
→
C322
→
Q309
→
IC201 Pin30
•
JK1 RING
→
L302
→
R333
→
C321
→
C323
→
Q309
→
IC201 Pin30
When the CPU detects a ring signal and press the “TALK” key on the handset, Q302 turns on and then Q301 turns on,
thus providing an off-hook condition (active DC current flow through the circuit) and the following signal flow is for the loop
current.
•
Tip
→
P0301
→
L301
→
D303
→
Q301
→
R303
→
Q302
→
D306
→
L302
→
Ring
ON HOOK Circuit:
Q302 is open, Q301 is disconnected 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:
CPU (Hook) turns Q302 ON/OFF to make the pulse dialing via Q301.
Make/Break ratio when dialing with the Handset 40% : 60%
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 Q304 is canceled by the side tone circuit C312, C313, R317, R318 and R319.
35
KX-TC2101BXB