Keyboard Wedge
This type of barcode reader is attached through the keyboard interface,
the barcode reader sends data in scan codes (the codes used by IBM PC
keyboards), exactly as you pressed the keys in the keyboard. It is called
“Wedge reader” because they physically wedge between the keyboard and
computer, as depicted the diagram below.
Since the barcode reader can use the power from the keyboard cable, no
external power is needed. On the other side, this configuration is not
designed for communication which has a distance more than 25 feet.
USB-based keyboard wedge
A special type of keyboard wedge barcode readers is the one using
now-popular USB technology. It is similar to the keyboard wedge reader
above, but uses the USB interface. No driver is needed too and the data is
placed directly in the keyboard buffer. It is convenient to use with a
notebook because the latter does not have an external keyboard.
Only Windows 98 or above platforms (including Windows ME, 2000 and XP)
supports USB configuration. The OS treats the reader as a USB keyboard and
automatically places the input in the keyboard buffer.
Keyboard Wedge interface is very simple to use. However, you must point
the cursor to the correct input box and make sure that the cursor always
stay in the right place before you press scan button. Theoretically a host
computer can connect multiple barcode readers using this configuration, but
the application has no knowledge about where the data comes from. Since the
barcode reader receives power from the computer, this type of configuration
does not need external power. The old application does not need to be
modified to accommodate this configuration.
Serial Port
The barcode reader is connected to one of the serial ports of the
computer. Software is needed to retrieve the information. It can be done in
your application, or you place some programs coming with the barcode reader
who simply reads the data and place them in the keyboard buffer. The
communication takes the standard RS232 or RS432. An external power adapter
is required for operation, and the distance can be as far as 250 feet. A
host computer can connect as many barcode readers as the number of serial
ports.
Windows provide a COM component called MSCOMM. Using this COM component
your application retrieve the data from the OnComm handler. Win32 also
provides serial communication APIs but this method requires advanced
skills.
Portable Batch
This type of barcode reader has memory powered by battery. Usually it
also has keyboard, LCD display and is programmable. The data is stored in
the memory first and then dumped into the computer via a dock station. The
data is usually transmitted in a comma-delimited text file format. The dock
station also acts a recharge station.
RF Cordless
Under this configuration a RF base station is connected to the computer
through keyboard wedge or serial interfaces. The barcode reader
communicates with the base station via radio frequency. The transmission
rates are in the 1200 to 4800 baud range. The battery usually lasts much
longer than the portable batch readers.
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