Panasonic KX-MB771GR Service Manual page 25

6.3.3. MODEM CIRCUIT OPERATION
The modem (Included IC300) has all the hardware satisfying the CCITT standards mentioned previously.
ALL processing is controlled by the SOC (IC300) according to CCITT procedures.
This modem (Included IC300) has an automatic application equalizer. With training signal 1 or 2 at the time of G3 reception, it can
automatically establish the optimum equalizer.
Facsimile Transmission/DTMF Line Send
The digital image data sent on ATXD line from modem (Included IC300) .
DAA IC100(6→9,10), Line side DAA IC101 and the NCU section to the telephone line.
Facsimile Reception
The analog image data which is received from the telephone line passes through the NCU section and enters line side DAA*
IC100. The signals are changed to digital data in IC100 (5,6) ,IC101(9,10→5) and IC300. In this case, the image signals from
the telephone line are transmitted serially. 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 con-
stant receiving sensitivity.
Busy/Dial Tone Detection
The path is the same as Facsimile Reception.
Call Tone Transmission
This is the call signal which is generated the SOC (IC300) and sent to the speaker.
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* DAA : Direct Access Arrangement
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