Xerox Phaser 6128 MFP, Service Manual

Page: 113 / 606

Phaser 6128MFP Service Manual 2-59
Theory of Operation
Control Circuit
The control circuit executes scanning of image data by controlling the image
scanner. A line of CCDs scans the original image one line at a time. When scanning
of one horizontal line is completed, the next line below is scanned. As this
continues, the original is scanned from end to end one line at a time and converted
to digital data as black-and-white information.
Because this image data is a set of digital signals, it cannot be transmitted using
an analog telephone line; it must be subjected to DA conversion (modulation). On
the other hand, the receiving Fax machine must perform AD conversion to restore
the incoming digital data to analog data.
DA conversion, analog signal transmission, analog signal reception, and AD
conversion are all performed by a modem (modulator/demodulator) in the control
circuit. A modem consists of a Network Control Unit (NCU) for connecting to the
telephone line and an A/D conversion unit for performing DA and AD conversions.
s6128-060
CCD
1 1 1 1 1 1
1 1 1 1 1 1
1 0 0 0 0 1
1 0 0 0 0 1
1 0 1 1 1 1
1 0 1 1 1 1
1 0 1 1 1 1
1 0 1 1 1 1
1 0 0 0 1 1
FAX System (Detail)
Scanner
Scanning
Lamp
Original
Original
Black becomes 0,
white 1 creating...
Digital data Image
Control Circuit
Digital Signal
Modem
DA
Conversion
(Modulation)
A/D Conversion
Unit
A/D Conversion
Unit
NCU
Analog Signal
Sending FAX
Telephone Line
Receiving FAX
Control Circuit
Modem
AD
Conversion
(Demodulation)
Printer
Digital Signal
Printing
Print