What is a Keyboard Wedge Barcode Scanner?

The KDC Line of barcode scanners work as a "Keyboard Wedge" solution for barcode data collection.

All Koamtac barcode scanners can work as "keyboard wedge" scanners. That means that the data from the scanned barcode, specifically the encoded ASCI characters are taken from the barcode scanner and placed or "streamed" so that they show up wherever the cursor is flashing. When operating in keyboard wedge mode, your barcode scanner is just special kind of keyboard that can only key in the numbers of the barcode that it reads. Its a little more complicated that that so if you have time, you can continue reading to get the functional particulars of the connection types and special capabilities of a keyboard wedge scanner. Or you can jump to the history of keyboard wedge scanning and interfaces.

HISTORY:

In the early days of the barcode scanner (the late 1970's), the ability to run systems programs like inventory, point-of-sale or warehouse management were limited to a mainframe or mini-computer. Entry of variable data like orders received or number of items counted in a warehouse bin were done using "green screen" terminals conected via RS232 cable to an interface board connected to the mainframe.

KoamTac Barcode Scanners are so powerful and versatile, they are literally the ONLY barcode scanner you'll ever need! The KDC line of barcode scanners will easily solve the "barcode scanning" part of your data collection problem. Here are just a few examples:

Before the advent of the personal computer, almost all tethered barcode scanners were connected to a serial port, and used some type of "middleware" (Keyboard Wedge software) to monitor the COM port to see if the scanner was sending data. The "middleware" then sends the ASCII text directly to the host's keyboard buffer or another location the user specified, to include changing the ASCII characters with parsing, suffixes or prefixes and terminator that the host system required to make the barcode data useful.

Lee Allen of Altek Instruments in the UK first used this technique back in the days before the PC was invented when small computers meant Apple IIs, Commodore Pets and CP/M systems. Nowadays the technique is firmly established and widely used in many situations but particularly for the collection of barcode data in real time.
Current Methods

The earliest Keyboard Wedges required intervention at the operating system level. A small unauthorised patch was put into the keyboard handling code. This method worked fine but is not usually appropriate for use today.

Nowadays most Keyboard wedge systems are hardware based.

Altek Instruments currently offer the following 'Wedge' solutions:-

The Mule (TM). A Hardware wedge system for the IBM PCs and keyboard compatible computers. Utilising Altek's proprietory KeyWedge technology for emulating PC scancodes. Its original use was connecting barcode scanners to PC computers but nowadays is widely used to connect all sorts of equipment- example weighing scales and other RS232 interfaced instruments.
The Multiplexer. A keyboard wedge system designed for RS232 terminals.
Most Barcode Scanners now include a built in keyboard wedge circuiit. This is the most popular way of connecting barcode scanners to PCs.

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A hardware device or software program that interfaces with a computer to translate data read by a device other than a keyboard, such as a magnetic strip or bar code reader or other such scanning device, into keyboard data. For example, data entered into a database via a bar code reader must first be translated into alphanumeric characters in order to be understood by the person interfacing with the database since humans do not read bar codes. The term wedge comes from the fact that the hardware device typically sits, or wedges, between the keyboard and the system unit. The keyboard is attached to the scanner, which is attached to processing component of the computer. Software wedges are programs that reroute the data once it has been input into a computer, typically through a COM port. The input data is routed to the keyboard buffer by the software, making it appear as if it entered the system through the keyboard. Keyboard wedges can be used simultaneously with keyboards.
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Keyboard Wedge Output

The "Keyboard Wedge" output option is the most common option. To interface a keyboard wedge bar code scanner to a PC, you would disconnect the keyboard from the keyboard port on the PC, plug the bar code scanner directly into the keyboard port and then connect your keyboard to a small "jumper cable" on the end of the bar code scanner cable (so that you do not lose the functionality of your keyboard). In other words, you are connecting the bar code scanner in the line between your keyboard and you PC. (One benefit of this is that the bar code scanner gets its power from the keyboard port so you do not need to connect any type of power supply to the scanner.)

When you scan a bar code with a keyboard wedge scanner, the data that is encoded in the bar code goes into the PC through the keyboard port so that it appears to whatever software is running in the PC as if it were being typed in on the keyboard. (i.e. The bar code scanner behaves exactly like a second keyboard connected to the PC.)
With a keyboard wedge scanner, you do not need any additional software. You simply plug the scanner in and start scanning bar codes. The keyboard wedge interface is extremely simple and in most situations, you do not need to make any changes to the software that you will be scanning the bar code data into.

The main advantage of the keyboard wedge interface is that it works just like a keyboard. You put the cursor where you want the bar code data to go and then scan the bar code and the data pops in just as if you typed it on the keyboard. The disadvantage of the keyboard wedge interface is that it works just like a keyboard. If the cursor is not in the correct input field in the correct application program, then, when you scan a bar code, the data still gets entered into the PC as if it is being typed in on the keyboard. If the cursor is not in the right place or if the application that you want the bar code data to go into does not have the input focus, the data goes to the wrong place or possibly the wrong application program. Also, if you need to modify the data in any way before it goes into the application program running in the PC, you cannot do this. For example, suppose that you need to parse the bar code data so that separate parts of the data goes to different input fields or if you want to add a date or time stamp to the bar code data, it is not possible with a keyboard wedge scanner.