Panasonic KX-FP342CX Service Manual page 173

are demodulated and converted into digital image signals. The communication format and
procedures for FAX communication are standardized by ITU-T. This1 chip modem (IC505) has
hardware which sends and detects all of the necessary signals for FAX communication.
It can be controlled by writing commands from the CPU (IC501: inside ASIC) to the register in the
modem (IC505).
This modem (IC505) also sends DTMF signals, generates a call tone (from the speaker), and
detects a busy tone and dial tones.
Overview of Facsimile Communication Procedures (ITU-T Recommendation):
1. ON CCITT (International Telegraph and Telephone Consultative Committee)
The No. XIV Group of ITU-T, one of the four permanent organizations of the International
Telecommunications Union (ITU), investigates and make recommendations on international
standards for facsimiles.
2. Definition of Each Group
- Group I (G1)
Official A-4 size documents without using formats which reduce
the band width of a signal are sent over telephone lines.
Determined in 1968.
Transmission for about 6 minutes at a scanning line density of
3.85 lines/mm.
- Group II (G2)
Using reduction technology in the modulation/demodulation
format, an A-4 size document is sent at an official scanning line
density of 3.85 lines/mm for about 3 minutes.
Methods to suppress redundancy are not used.
Determined in 1976.
- Group III (G3)
Method of suppressing redundancy in the image signal prior to
modulation is used. An A-4 size document is sent within about one
minute.
Determined in 1980.
- Group IV (G4)
Transmission is via the data network. A method is provided for
suppressing redundancy in signals prior to transmission, and error
-free reception of transmission is possible.
The scope of these facsimile applications is not limited simply to
transmission of written statements. Through symbiotic linkages
with other communication methods, it can be expected to expand
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