Barcode Reader Connection Principles
A set of barcode reading equipment usually consists of two main components - the reader (also called the decoder) and the scanner. The scanner reads the code and the decoder interprets it and presents the characters contained in the code to the host computer. With most modern desktop barcode readers the decoder is integrated into the scanner.
As regards connection to the computer, the characters in the barcodes that the equipment reads are transmitted through the keyboard port, through a serial port, through a USB port, via a custom cable to specific tills, or even radio frequency or infra red. The most common methods are keyboard, USB or serial connections.
The keyboard wedge method involves a special splitter cable. The keyboard is connected at one end of the cable and the other end plugs into the keyboard port on the computer. The scanning equipment is then connected in the middle of the cable and therefore 'wedged' in between keyboard and computer. Keyboard operation is unaffected and when a barcode is scanned the characters in the code appear on the computer screen at the cursor position as if it had been typed in very quickly. Most scanners also allow the automatic addition of characters before or after the barcode, for example to advance the cursor to the next screen position. The keyboard method of barcode scanning requires no alterations or additions to application software and will work with virtually any pc.and many common types of network terminals.- Wyse, IBM, Dec. etc.... USB barcode scanners also emulate the keyboard using drivers supplied within Windows based operating systems. Connection cards are also available on some scanners for CE based palm held computers.
The serial (or RS-232 ) method of connection is necessary when your software or equipment is expecting communication via the serial port - for example retail tills or RS-232 Unix networks - though connection to a normal pc is possible providing there is software in operation that will read input from the serial port. With serial connections, siting of the reader and scanner is also possible at greater distances from the pc than with the keyboard wedge connection, though mains power to the scanner is normally required. JJA also supply interfaces and software to connect all the major scanner types to laptop and even Windows CE palmtop computers.
This site does not contain information about the construction or history of barcodes or how they work, but an excellent link to this area of information is HERE.