Xerox Phaser 6180MFP, Service Manual

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Phaser 6180MFP Multifunction Printer Service Manual 2-97
Theory of Operation
Fax (Facsimile) System Overview
A Fax is a device that sends and receives image data using either an analog
or a digital telephone line.
The three basic units of a Fax are the Scanner (for reading the image), the
Control Circuit, and the Printer.
The scanner splits the image into a fine grid and reads the brightness (white/
black) of each cell. This operation is called scanning. The white/black
information is converted to a digital signal: bright cells become 1, dark cells
become 0.
The digital signal from a scanned image is subjected to DA conversion
(modulation) by the control circuit to enable transmission over an analog
telephone line. After conversion, the data is sent as an analog signal. The
sound audible during transmission is image data that has become an analog
signal, that is, an audio signal.
The analog signal arriving over the telephone line is then subjected to AD
conversion (demodulation) by the control circuit of the receiving Fax machine,
and restored to a digital signal.
The black/white information obtained from the AD conversion is sent to the
printer, where black cells are reproduced on the paper at the positions where
they were on the original.
s6180mfp-105
Fax System (Overview)
Image Scanner Control Circuit Control Circuit Printer
Scanning Printing
DA
Conversion AD
Conversion
Telephone
Line
Original
Digital Signal Analog Signal Digital Signal
Printing