NCR RealScan 7892 Bi-Modal Presentation Scanner

Chapter 4: Operating Your Scanner 4-9
Distance from Scanner
For optimum reading, the distance you must place the label from the
RealScan 7892 depends on the density and height of the bar code. You
can relate this to focusing a camera, where you change the focus setting
based on how far away the object is.
Depending on the label, reading can range from zero to six inches.
Therefore, when you use your scanner, move the label toward the
scanner to a comfortable distance in front of the scan window
(approximately three to four inches) and hold the item momentarily.
Normally the "Good Read" indication occurs within one fourth of a
second. If this does not happen, try moving the label a little closer to
the scanner.