Appendices
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MS-850 Raster Scanner User’s Manual
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Appendix D — Position Object Detector
In a typical operation, a scanner will wait for bar code data only during a triggered
read cycle. A read cycle is initiated by a “trigger” and can be in the form of a serial
command from the host (internal trigger) or a signal from an object detector (exter-
nal trigger).
When an object detector is used, it is set up so that its beam will bounce off the
approaching object and the resulting pulse will be sent to the scanner to begin the
read cycle. Typically, a detector is positioned so that it will detect the presence of an
object before its label can be scanned.
An object detector is mounted in almost any position relative to the object as long
as (1) the object passes within range of the detector and (2) direct or reflected light
from the detector does not interfere with the scanner’s reception.
As the item continues to move down the line, its label moves into the scanner beam
and is read by the scanner.
The drawing below shows a label in the picket fence direction with the object detec-
tor positioned so as not to cause interference.
S can n e r
S can b eam
Lab el
D et ec tor
D irec tion of
lab el trave l
