Symbol PDT 7500 Series Product Reference Manual page 55

Operating the Terminal
scan pattern extends at least three-quarters of an inch beyond the edges of the bar
code.
Figure 4-2. Slab Raster Pattern on a PDF417 Bar Code
3. If the pattern is parallel to the symbol's rows, the pattern spreads vertically to cover
the symbol (Figure 4-3). If the pattern does not cover the top and bottom of the
symbol, pull the scanner back until it does.
3/4"
3/4"
Figure 4-3. Scanning Pattern Spreading Over PDF417 Bar Code
4-9