Worth Data P11/12 - Manual (Page 14)

2-8
Preamble
A "Preamble" is a user-specified data string transmitted at the beginning of each bar
code. For example, if you specify the preamble @@ and read data of 123456,
"@@123456" would be transmitted to your computer.
The default is no preamble. To select a preamble, scan up to 15 characters from
the "FULL ASCII MENU" on the back of the Reader Setup Menu, and then scan
SET when you're done. To return to the no preamble setting, scan CLEAR here
instead of scanning SET or any characters from the FULL ASCII MENU.
You can trim 1-15 leading characters from bar code codes by scanning a ~ (tilde --
ASCII 126) followed by a single digit, 1 through F (A through F are for 10 to 15),
as part of the Preamble. (Bar codes which are shorter than the amount-to-trim are
transmitted with no trimming.) Consider the examples in the following table to
understand how trimming works:
Bar Code Data Preamble Data Transmitted
123 XYZ XYZ123
12345678 ~3XYZ XYZ45678
12345678 ~9 12345678
12345 ~A ~A12345
123456 ~5 6
You can also trim selectively by bar code type. For example, you can trim 2
characters from Code 39 and a different amount from other bar code outputs. This
is done by using the bar code ID character in conjunction with the tilde. A
preamble of ~b2~c1 says trim 2 characters from the front of Code 39 output and
trim 1 character from the front of UPC-A. Refer to the Code 128 parameter's
previous discussion for a list of the ID character associated with each bar code type.
For advanced PC users: Emulating special keys in the preamble:
Programmers and other advanced PC users can also embed keyboard hex scan codes
in the preamble, for emulation of key presses specific to their computers, such as the
left shift key or F12 key. This is done by specifying the make and break hex scan
codes for one or more keys enclosed in "left" and "right" apostrophes (` and ').
Make and break codes are hardware-specific -- see the keyboard section of your
computer's manual or tech references for descriptions of its make and break codes.
Break codes follow one of two conventions depending on which "keycode set" a
keyboard uses. Keycode set 1 (usually on XT-style systems) uses a two-digit break
code formed by adding hex 80 to the make code. Keycode set 2 (usually on AT-
style systems) uses two digit break codes: the first is F0 and the second is identical
to the make code.
For example, let's say you want to emulate the left shift key. First, using the FULL
ASCII MENU, you'd scan a left apostrophe, to identify subsequent characters as
keyboard scan codes. Next, the two-digit hex make code -- let's say it's 12. First