COPYRIGHT © 2002 CANON INC. CANON FAX BOARD REV.0 MAR. 20022 - 2CHAPTER 2 BASIC OPERATION1.2 Functionsa. Image Processor PCBCommunication Control BlockThe communication control block is designed to detect circuit signals (e.g., CNG,DTMF). It also uses the main CPU on the image processor PCB to control the 33.6kbpsmodem, thus modulating or demodulating transmission/reception data.Memory FunctionThe 16MB (as mounted) SDRAM used for storage of image data is capable of holdingimage data equivalent to about 100 pages (about 2 MB) of Canon FAX Standard ChartNo. 1. The image data will also be backed up for about 1 hr by the vanadium lithium sec-ondary battery in the event of a power shortage. The 128KB SRAM, on the other hand, isdesigned to store registered data (e.g., user data, service data), and the data will be backedup by means of a lithium battery when the machine is turned off (for about 5 yr).Image Storage DIMM Slot (option)The RAM-DIMM (32MB x 2) fitted to the slot is used for storage of image data fortransmission and reception.b. NCU PCB2-line/4-line Conversion CircuitThe signal from a 2-line type telephone line is converted into transmission signals andreception signals (4 lines). It also prevents transmission signals from the modem fromcoming into the reception circuit.Dial Pulse Generating CircuitThe dial pulse generating circuit is designed to generate dial pulses by turning on andoff the relay inside the circuit in response to the control signal from the image processorPCB, thus sending the dial signals from the fax using the telephone line.Off-Hook Detection CircuitWhen the telephone line connected to the telephone terminal or the handset (option) isin off-hook state, the direct current flowing to the circuit is detected to find out that thesystem is in off-hook state.Line Voltage Conversion CircuitThe primary side of the NCU PCB is controlled by a +48V DC circuit voltage; its directcomponent is cut using a capacitor so that only the voice signal is connected into a mo-dem-level voltage.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 forcommunication of signals from a fax to the telephone line.
