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What is a Keyboard Wedge Barcode Scanner?

The UnionNet SP2100 Line of barcode scanners work as a "Keyboard Wedge" solution for barcode data collection.

All UnionNet / BarcodeGuy SP2100 barcode scanners can work as keyboard wedge barcode scanners. That means that the scanned data from the barcode is sent to the host and shows up where the cursor is flashing. The "wedge' part is a literal way barcode scanners were connected. Whatever cable went from the keyboard to the "box" was modified so that it was a Y with the keyboard on one side and the barcode scanner on the other.

In today's parlence, HID is the same as keyoard wedge. Technologically though what's changed is that the "box" (yep, your phone is one) was able to handle having multiple keyboards and other input devices attached. You can click to read the technical stuff about different connection types. On this page, we're only concerned with explaining the function and history of the term 'keyboard wedge'.

BarcodeGuy SP2100 Keyboard wedge barcode scanners

Each of the SP2100 line can work as Keyboard Wedge Scanners.... via a Bluetooth connection!

Most Keyboard Wedge Barcode Scanners are connected via USB when you're talking about PC's...

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Buy Keyboard Wedge barcode scanner - BarcodeGuy SP2100!

Barcode USB HID Connection
Barcode Scanner USB HID / Keyboard Connection

Pretty simple, isn't it? As it turns out, its not as simple as it seems. The most common barcode scanners on the market today plug into a USB port on the host PC or Mac. When you plug in the scanner, the computer's operating system talks to the USB port to find out what was just plugged in. The barcode scanner has been pre-programmed to answer the PC or Mac that it's a "just another keyboard" or HID (Human Interface Device). Because the barcode scanner follows the conventions of a standard computer keyboard and the computer makes the connection and routes all data coming from the barcode scanner right to the keyboard buffer, when you scan a barcode the data entry process acts like you just typed in the characters on the keyboard. The barcode scanner will commonly send a Carriage Return at the end of the string of scanned characters, which is the same code that the computer sees when you press the enter key. The barcode scanner pulls power from the USB port. But that USB connection we've been talking about? ...

Keyboard Wedge Scanners Got Their Name Before Before USB Scanners Were Invented...

Barcode USB HID Connection
Keyboard Wedge Barcode Scanner Connection

Keyboard Wedge Barcode Scanner Detail

Detail of "Wedge Cable" for early Keyboard Wedge Barcode Scanner

Well, USB connections didn't exist back in the early 90's. With the advent and refinement of the personal computer (back before Windows 98) there was an increased demand for the ability to use barcode scanning technology as a replacement to keyboard entry in worksheets, databases and application programs where keying in the "stuff" as laborious an had a fairly high error rate. The problem was, early PC hardware only had one method to connect a keyboard - the physical AT or PS2 keyboard port on the back of the computer. No other keyboard connection to the host was available and therefore, there was no other way to get data to the keyboard buffer of the new MS Dos machines.

Engineers for corded barcode scanner companies used a clunky but straightforward method to overcome the problem. First, they programmed the non-volatile and persistent firmware on the scanner to mimic keyboards, and included options for changing things like the terminator, what symbology barcodes allowed and even rules for adding suffixes, prefix and data formatting rules to the scanned characters to the firmware.... programmable by scanning set-up barcodes for the barcode scanner in question. Then they made the scanner output (what was send down the cord) compliant with data output standards of the keyboards of the day. But a final problem remained.... how to get the data into the host?

The problem was solved in a pretty blunt way that can be alternately viewed as being primitive and elegant... they made a "Y" cable. The bottom of the "Y" plugged into the computer's AT or PS2 keyboard port. At the top of the "Y", one side of the cable connected to the barcode scanner, the other end had a PS2 or AT connector to plug in the keyboard. In effect, the barcode characters were "wedged" into the keyboard cord, hence the term "Keyboard Wedge". Most often, power for the barcode scanner came from an external power supply. But remember that PS2 or AT keyboard connector were were talking about? ...

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Buy the SP2100 keyboard wedge barcode scanner

Before Keyboard Wedge Barcode Scanners - Data From Barcode Scanners Came From a Serial Port....
Keyboard Wedge Barcode Scanner

As you can see by this Detail Drawing, Serial Connected Keyboard Wedge Barcode Scanners have an external Power Supply and connect to a 25-pin or 9-pin Serial COM Port on the back of the host PC

Before the advent of the personal computer (we're talking mainframe and mini-computers here), communications between the host and attached device (even the early equivalent of the disk drive) took place using serial communications. Anything you attached - screen, keyboard, modem, tape drive, etc. were most likely attached using a serial port. Barcode scanners were no exception & a small piece of software ran on the terminal to monitor the serial port. When barcode characters showed up in the COM port, the software put it where it was told to. In the early days of the barcode scanner (the late 1970's), mainframes and mini's were dedicated to "accuracy systems" like inventory, point-of-sale & warehouse management to justify their costs. Early barcode scanner salesmen touted the need for their products to speed key entry and eliminate data entry errors. Since most all applications needed to use the barcode data as a substitute for keyboard entry, this software came to be known as "Keyboard Wedge" software.

And now we've come full circle. The HID connection of our SP2100 is a variant of the keyboard wedge software that routed barcode characters before physical keyboard wedge cables or USB cables with HID recognition.... only much more powerful. You can perform barcode data formatting such as prefixes and suffixes and whether the barcode characters will be followed by a date/time stamp or scanner serial number and a host of other settings that in essence format the barcode data as it is sent to the host.

And remember....

If you need a quick, simple, powerful, high-speed method to collect barcode data, the SP2100 Line of Barcode Scanners is your best choice! Take a look at our Product Comparison / Pricing Page . Or just give us a call and we'll help you any way that we can.


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