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Operation Board
Photo transistor
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5.6. MODEM SECTION
5.6.1. FUNCTION
The unit uses a 1 chip modem (IC1), enabling it to act as an interface between the control
section for FAX sending and receiving, and the telephone line. During a sending operation, the
digital image signals are modulated and sent to the telephone line. During a receiving operation,
the analog image signals which are received via the telephone line are demodulated and
converted into digital image signals. The communication format and procedures for FAX
communication are standardized by ITU-T. This 1 chip modem (IC1) has hardware which sends
and detects all of the necessary signals for FAX communication and DTMF. / It can be
controlled by writing commands from the ASIC (IC1) to the register in the modem (IC1). / This
modem (IC1) also sends DTMF signals, generates a call tone (from the speaker), and detects
busy tones, dial tones and DTMF.
Overview of Facsimile Communication Procedures (ITU-T Recommendation):
Signal (CN2-5
Pin)
ON
Low level
OFF
High level
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