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Page12 AllAboutBarCodes

a “serial eavesdrop” cable to connect the scanner between the terminal and the host computer When using serial scanners

with PCs, keep in mind that your application needs to “monitor” the serial port for incoming data Most applications do not

do this, and so an additional piece of software, called a “software wedge”, may be required

Operating Systems

Once you have decided on the scanner technology, you must design the system These systems can be set up in several

congurations Some applications will work with only one particular system type, but most applications allow you to select the

system to meet the best cost/performance requirements The basic system types are:

Single User: These systems use a single PC with a single bar code reader to process data These are generally the best type

of system to start with, as they give you experience with bar code technology without some of the complexities of multi-

user systems An example of a site with a single-user system is a small video store that uses a wand to read bar codes on

movies and stickers on customer cards The store might also use a slot scanner for customer cards

Multi-user: This was once the most common type of system It consists of a single computer that is hooked to several bar

code readers, terminals, or both A multi-user operating system manages the data collection

Local Area Network: These systems connect several essentially single-user systems and a common le server using a

network These are the most exible systems and currently the most popular

Portable Systems: Prices of portable data terminals and mobile computers have fallen over the last few years, making

portables one of the best solutions for bar code applications Portables are used with computers to keep data current either

in real time or in batch mode

Single-User Systems

A single-user system is simply a PC with a bar code scanner attached The system generally uses a wedge to simulate keyboard

input A wedge can be used with any PC that has the same keyboard interface as the wedge Most computers have either a DIN

connector (like that on IBM computers through the AT) or a PS/2-style keyboard connector A few companies make their own,

nonstandard keyboard connectors You must be sure to get the right kind of wedge for the computer you are using

The normal action of a bar code reader is to simulate typing the keystrokes for the characters in the bar code and then press the

Enter key You can change the Enter key to a tab key or any other key for specic situations

When the reader must be remote from the PC or terminal, you can later connect it reader to a serial port and use a “software

wedge” to send the data into the keyboard buffer Another possibility is to write the application so that it monitors the serial port

for incoming data Serial decoders are also useful if you must support a computer that uses a nonstandard keyboard interface

And when you want to use a single bar code reader with a combination of PC, Macintosh, or UNIX systems Software wedges

are available for a variety of operating systems

Multi-User Systems

Multi-user systems have traditionally been the most common type of bar code system This system uses serial ports to connect

a single PC or other computer system to multiple bar code readers, terminals, or both Each terminal runs a single session on the

multi-user operating system Cheaper PC prices and the availability of very basic network PCs will undoubtedly sway some users

away from multi-user systems Clearly the multi-user system is on its way out

This type of system requires a multi-user operating system If you want to use terminals with bar code readers attached to

them, you can use any multi-user operating system, such as DR Multi-user DOS, VM-386, or UNIX

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Datalogic Hand-held devices II Especificaciones Pagina 12