7.3.4.2. MODEM CIRCUIT OPERATION
The CODEC (IC609) and ASIC (IC604) has all the hardware satisfying the CCITT standards
mentioned previously.
ASIC (IC604) controlled codec (IC609 by senial data.
This CODEC (IC609) and ASIC (IC604) has an automatic application equalizer. With training
signal 1 or 2 at the time of G3 reception, it can automatically establish the optimum equalizer.
1. Facsimile Transmission/DTMF Line Send
The digital image data on the data bus is modulated in the modem
(IC602), and sent from pin 69 via modem IC602, Analog gate array
IC201(24 22), amplifier IC207(2 1) and the NCU section to the
telephone line.
Refer to CHECK SHEET().
2. Facsimile Reception
The analog image data which is received from the telephone line
passes through the NCU section and enters pin 14 of the CODEC
(IC609). The signals that enter pin 14 of the CODEC (IC609) are
demodulated in the board to digital image signals, and then senol
pin p1 of the ASIC (IC604).
In this case, the image signals from the telephone line are
transmitted serially. In the ASIC (IC604). Here, the internal
equalizer circuit reduces the image signals to a long-distance
receiving level.
This is designed to correct the characteristics of the frequency
band centered around 3 kHz and maintain a constant receiving
sensitivity.
It can be set in the service mode.
Refer to CHECK SHEET().
3. DTMF Transmission (Monitor tone)
The DTMF signal generated in the ASIC (IC604) is output from pin
P3, and the NCU section to the telephone line the same as
203
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