Philips SpeechMike Scanner 6284 Advanced Configuration Guide page 89

Tolerance
TxD
UPC
Visible Laser Diode
(VLD)
Allowable deviation from the nominal bar or space width.
Transmitted data.
Universal Product Code. A relatively complex numeric symbology.
Each character consists of two bars and two spaces, each of which
can be any of four widths. The standard symbology for retail food
packages in the United States.
A solid state device which produces visible laser light. Laser light
emitted from the diode has a wavelength of 670 to 680 nanometers.
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