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Part 4: Technical Reference
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.
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.
Infrare
Figure 4-9 IrDA
The ASK format is used by Sharp's Zaurus.
Optical Filter
LED
Infrared Transmitter
Infrared Receptor
Photo Diode
4-12
BJC-50
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