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Refer to
CHECK SHEET
5. Busy/Dial Tone Detection
The path is the same as FAX receiving.
5.7. ANALOG UNIT BLOCK DIAGRAM
5.8. NCU SECTION
5.8.1. GENERAL
This section is the interface between the telephone line and external telephone. It is composed
of an EXT. TEL Line relay (RLY1), bell detection circuit, EXT TEL selection circuit, pulse dialing
circuit, line amplifier, sidetone circuits and multiplexer.
5.8.2. LINE RELAY (RL1)
Circuit Operation
Normally, this relay switches to the external telephone side (Break) and switches to the open
side (make) when the unit starts facsimile communication. Pulse dialing is also performed by ON
/OFF of the relay.
[IC1 (99) High Level
5.8.3. BELL DETECTION CIRCUIT
Circuit Operation
The signal waveform for each section is indicated below. The signal (low level section) input to
pin 19 of ASIC IC4 on the digital board is read.
TEL LINE
PC1 (1, 2 - 4)
5.8.4. PULSE DIALING
[IC1 (99) High Level
Refer to # 013 on the
5.8.5. LINE AMPLIFIER AND SIDE TONE CIRCUITS
1. Circuit Operation
The reception signal received as output from line transformer T2
is given as input to C23, R33 and IC2 pin (6). / Then it is input to
the reception system at an amplifier gain of 5.9 dB from pin (6). /
The transmission signal is input from CN1 pin (11), and output to
the TEL line through C30, R31 and T2. Without a side tone circuit,
()
CN9 (8)]
CN1(8)
CN1(6)
[CN9(6)
CN9 (8)]
CN1 (8)
PROGRAM MODE TABLE
Q3 ON
RL1 (make)
R119
IC1(56)]
Q3 ON
PC1 ON (make)
()
156
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