COPYRIGHT © 2002 CANON INC. CANON FAX BOARD REV.0 MAR. 20022 - 4CHAPTER 2 BASIC OPERATION1.4 Functionsa.G3 Multiport PCBCommunication Control BlockThe communication control block is designed to detect circuit signals (e.g., CNG,DTMF). It also uses the CPU on the image processor PCB to control the 33.6Kbps mo-dem, thus modulating or demodulating transmission/reception data.Memory FunctionThe 16MB (as mounted) SDRAM used for the storage of image data is capable of stor-ing image data equivalent of about 100 pages (about 2 MB) of Canon FAX Standard ChartNo. 1. The image data is backed up by a vanadium lithium secondary battery for as longas 1 hr in the event of a power shortage. The 128KB SRAM, on the other hand, is used toback up registered data (user data, service data), and its contents are backed up by meansof a lithium battery when the machine is turned off (as long as 5 yr).Image Storage DIMM Slot (option)The RAM-DIMM (32MB x 2) fitted to the slot is used for storage of data for transmis-sion and reception.b. NCU PCB2-line/4-line Conversion CircuitThe 2-line signal from the telephone line is converted into 4-line signals (transmissionsignal and reception signal): it also prevents the transmission signals from the modemfrom coming into the reception circuit.Dial Pulse Generating CircuitThe dial pulse generating circuit is designed to generate dial pulses by turning on andoff the relay in the circuit, thus detecting dial signals from the fax over the telephone line.Off-Hook Detection CircuitWhen the telephone connected to the telephone terminal or the handset (option) is inoff-hook state, the direct circuit flowing to the circuit is detected to find out if the systemis in off-hook state.Line Voltage Conversion CircuitThe primary side of the NCU PCB is controlled by a circuit voltage of +48 VDC; itsDC component is cut, and only the voice signals are converted to modem-level voltages.c. Modular PCBTelephone Line InterfaceThe signals from the 3 modular jacks (for telephone line, for telephone connection, foroption handset) is forwarded to the line voltage conversion circuit of the NCU PCB,thereby communicating the signals from the fax to the telephone line.
