Refer to LS1900 REFERENCE manual provided on CD with scanner for page numbers. Other models have similar PDF manuals (LS2208, etc).
Not all LS1900 scanners come properly programmed from the factory. When attempting to scan a barcode, there is a "beep" but no text appears. To program, you must print the following pages from the LS1900 Reference Guide: 4-10, 4-117, 4-118.
On page 4-10, scan "Set All Defaults"
On page 4-117, scan "Scan Option", "Data Suffix"
On page 4-118, scan "Enter"
The scanner should now be programmed correctly.
On other model Symbol scanners search the PDF for the word "return" and print out the page with 3 scan codes to add a carriage return at the end of the scan.