Table of Contents
Advertisement
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
R124
D106
- The receiving signal flows:
TEL line
POS101
Q405
Q406
- The transmission signal flows
Mic
Q421
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
Q201
When the subscriber hangs-up, check the intermittent tone. If cycle tone is detected, the collector
of Q201 goes to a low logic.
POS101
D101
R
Q101
Speaker
Q424
C435
R201
R205
D101
C113
R125
R437
Q108
Pin 5 of IC201
Pin 1 of IC201
22
Q101
Q108
C108
Q109
POS101
D202
Tel
R208
Advertisement
Table of Contents
