Datalogic Hand-held devices II Dokumentacja Pobierz pdf (Strona 11)

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Laser Scanners: These are the best type of input device and are therefore the most expensive of the hand-held options

They will work with curved or uneven surfaces and will read most very low quality bar codes They will also read over a

much greater distance than wands or CCDs, usually 5” to 27” (I2 to 65 cm) Laser scanners come in general-purpose and

heavy-duty versions

In and/or On-Counter Laser Scanners: These systems use laser readers that are xed in place, and the bar codes are

brought to the scanners The most common example is the scanners in used in grocery stores Another example is a

conveyor controlled xed-mount laser scanner that reads the labels on boxes or packages as they move down a line These

are used in the airline industry to process baggage, in warehousing to control conveyors or other devices, and in many

types of manufacturing

Slot Scanners: Slot scanners are used for time-and-attendance, security, and other systems Each scanner has a slot that

you slide bar-coded cards through These scanners look much like the credit card readers you see in retail settings, but they

read bar codes instead of magnetic coding

Combination Scanners: You can frequently mix two different types of input devices For example, you can attach a slot

scanner and a laser scanner to a decoder to allow users to enter information either way Many models allow you to attach

magnetic card scanners to bar code readers This way, you could process credit or ATM cards with the same system that

reads bar codes on packages

Interfaces

Once you have selected an input device, you must select a decoder and the type of interface to the computer Most batch

systems use a periodic download over serial ports, and you don’t have much choice in the interface method Interactive systems

have a choice of several interfaces

When choosing the interface, you must keep the following factors in mind:

Existing equipment: If you plan to use existing equipment (computers, terminals, etc), you will need to make sure the

interface type you choose is compatible with the equipment you currently have

Data Reliability: Interface types vary in ease of use One interface may allow the user to affect the data, while another may

not This does not mean that one interface type is inherently better than another It does mean that where user error can

affect data, more follow-up will be required

Locations of Readers: The location of the readers can have a profound impact on the design of the system For example,

most shop oor environments are too crowded or are unsuitable for PCs This limits the type of system interface you can

use As with the input device, you should test the system architecture you choose in as many real-world conditions as

possible

Interfaces come in these basic types:

Interactive Systems

Wedge Readers: These systems are the least expensive and the easiest to implement The bar code reader connects

between the keyboard and the computer and simulates keyboard input The application program does not know the

difference, and the user can always type in the numbers if the bar code is unreadable This is the best choice in many cases

Serial Readers: These systems are more exible than the ones using wedge readers In this case the reader is connected

to the computer or terminal over a serial port to the computer Since serial communication is standardized, you can typically

use a serial decoder with almost any computer or terminal (cabling may vary) Serial readers are ideal for terminals, since

most terminals are serial devices themselves If your terminal does not have a port available for a serial scanner, you can use

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Datalogic Hand-held devices II Dokumentacja Strona 11