Canon BJC 50 Service Manual - Page 100

Part 4: Technical Reference BJC-50 2.1.4 IrDA IrDA is an IrDA (1.0) conforming infrared serial communicating device that is built-in on the back side of the printer. Input and output of infrared light is conducted through this device. For wireless infrared one-to-one communication, the computer's IrDA and the printer's IrDA must be facing each other. The infrared light emitted from the IrDA travel sideways and lengthwise as sown in Figure 4-9. The forward direction is the light axis. As the infrared light travel sideways and lengthwise in a two dimensional plane, the intensity of the light along the light axis decreases disproportional to the square of the distance between the IrDAs. The IrDA standard establishes the infrared emission intensity and the receptor sensitivity to ensure quality transmission. The IrDA transmission end should be located within the shown circular cone. [distance: 1 m, angle: 15Þ from the light axis] The infrared transmitter and the receiver are integrated into one unit. Optical Filter LED Infrared Transmitter Infrare Infrared Receptor Photo Diode Figure 4-9 IrDA a) Transmission formats There are two transmission formats, the base band transmission and the variation transmission. In base band transmission, the RZ signals that represent bit data control the ON/OFF of the infrared light. When the data is "0" in the IrDA mode, infrared rays are emitted only for a duration of 3/16 of the time required to send 1 bit of data. In variation transmission, the amplitude of the infrared carrier frequency is varied depending on the digital data. (ASK format) Infrared light with a peak wavelength between 850 nm and 900 nm is switched on and off at 500kHz to be used as a carrier frequency. The ASK format is used by Sharp's Zaurus. 4-12