Panasonic KX-TS105LXW, Service Manual, Page: 22 / 44

Q101 turns on thus providing an off-hook condition (active DC
current flow through the circuit) and the following signal flow id for
the DC loop current. T POS101 D101 Q101 Q108
R124 D106 D101 R
- The receiving signal flows:
TEL line POS101 Q101 C113 R125 C108 Q109
Q405 Q406 Speaker
- The transmission signal flows
Mic Q421 Q424 C435 R437 Q108 POS101 Tel
Line
11.3.3. Tone Detect
This circuit is used to sense the status of the line (busy tone or dial tone) during Auto Redial.
11.3.3.1. Circuit operation
D101 Q101 C201 R201 R205 Pin 5 of IC201 Pin 1 of IC201 D202 R208
Q201
When the subscriber hangs-up, check the intermittent tone. If cycle tone is detected, the collector
of Q201 goes to a low logic.
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