Phaser 6180MFP Multifunction Printer Service Manual 2-97Theory of OperationFax (Facsimile) System OverviewA Fax is a device that sends and receives image data using either an analogor a digital telephone line.The three basic units of a Fax are the Scanner (for reading the image), theControl 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/blackinformation is converted to a digital signal: bright cells become 1, dark cellsbecome 0.The digital signal from a scanned image is subjected to DA conversion(modulation) by the control circuit to enable transmission over an analogtelephone line. After conversion, the data is sent as an analog signal. Thesound audible during transmission is image data that has become an analogsignal, that is, an audio signal.The analog signal arriving over the telephone line is then subjected to ADconversion (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 theprinter, where black cells are reproduced on the paper at the positions wherethey were on the original.s6180mfp-105Fax System (Overview)Image Scanner Control Circuit Control Circuit PrinterScanning PrintingDAConversionADConversionTelephoneLineOriginal Digital Signal Analog Signal Digital Signal Printing
