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For 30 years I have been helping organisations and individuals with their Barcode and Auto ID issues but now I have decided it is time to move on and retire from being the Barcode Man.

I will continue to respond to emails from existing customers about their earlier purchases, their special programming configurations and warranty issues but I regret I cannot help with new purchases or issues nor recommend alternative products or sources.

Lee Allen, The Barcode Man. February 2010

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The Mule™

Product Discontinued: We regret that owing to supply difficulties The Mule is no longer available

What is The Mule? - Summary

  • The Mule converts RS232 ASCII data into scancodes which the computer interprets as keystrokes. It can act as a 'virtual keyboard' by emulating a keyboard directly in hardware (KeyWedge Mode) or can utilise the USB port to achieve similar results utilising the Human Interface Driver (HID) provided with most modern operating systems.
  • The Mule can be used to simplify the interconnection of devices such as Barcode Scanners, Weighing Scales and other technical instrumentation to applications software even if the software authors had not anticipated the need for such interoperability.
  • The Mule can be used to allow one computer to control another. This has wide application in industrial, technical, scientific, manufacturing and testing environments.

The Mule and KeyWedge are trademarks of Altek Instruments Ltd

The Mule Interface


[Jan 2007] Keyboard Emulator now On-Line

The Mule can create any combination of key strokes but for non ASCII keys you need to know the scancodes. This used to mean looking them up individually in a table and then working out the up and down sequences you needed. Now you can build the sequences you need for the most exacting applications just by clicking on the keys in an emulator. The Keyboard Emulator works exactly like a real keyboard and is free for all to use. You can try out any combinations of keys and read out the scancodes produced in real time. Cut and paste direct into your application to recreate the keystrokes by sending them direct to The Mule. Link to the Keyboard Emulator

[July 2004] The Mule gets a USB interface

The Mule can now work with USB Keyboards in exactly the same way as regular keyboards. This means easier use with laptops and portables and the ability to work with non PC architecture computers like the Apple Mac.

[Sept 2003] The Mule can handle the New Keys

Keys like Sleep, Power and Wake Up are now detailed in the updated scancode table. The Mule can emulate all of them.


The Mule is a clever device designed to allow a RS232 peripheral to send its data to any applications program running on a PC. The Application does not need to understand about the peripheral device nor have any special provision for handling the data from it. The Mule links the computer to the peripheral in such a way that the data appears to be coming from the keyboard.

Originally designed to simplify the attachment of barcode scanners to PCs, The Mule has now found widespread use interfacing many different types of RS232 based peripherals to PCs.

The Mule is connected between the keyboard and computer. RS232 data is converted into keystrokes and appears in your applications program just as if the data was typed. It works with any program running under any operating system now or in the future. Windows, DOS, Unix...The Mule works with them all. Normal keyboard operation is unaffected.

The Mule is designed to be simple, easy to understand and unobtrusive. No technical knowledge is needed and no tools are required to attach The Mule to a PC. There are no software drivers and it is not necessary to open the computer case. The Mule does not interfere with the normal working of a PC.

Users do not have to learn new techniques or adopt new working practices.

Background: RS232

The RS232 Serial interface has been used as a means of interconnecting computer equipment since the earliest days. Despite the fact that many 'improved' interface specifications have been proposed as a replacement, none have been widely adopted and the RS232 interface is still being designed into many computer peripherals.

Background: PC Interface limitations

Over the last decade the modern PC has evolved dramatically in terms of processing power. However the facilities for attaching peripheral devices have hardly improved since the mid 1980s. A modern PC probably has two RS232 ports but should you want to use them for anything other than a mouse or modem you would most likely need engineering knowledge to make it work and also have support from the Application program. If the Application is not specially written to handle RS232 data it is sometimes virtually impossible.

Background: Wedge interface techniques

A 'Wedge' interface is a means of introducing data into an existing data stream- in this case the keyboard input channel. The technique was developed in the early days of 'Home Computers' by Lee Allen at Altek in the years before IBM introduced their first PC. Altek use the trademark 'KeyWedge' to describe their proprietary 'Keyboard Wedge' interface. A KeyWedge interface can be implemented in Software or Hardware. The Mule is the latest hardware implementation from Altek and it supersedes earlier 'software only' methods. A hardware implementation is better because it is independent of the computer operating system. It works with All versions of Windows, DOS and any other operating system- past or in the future. Detailed technical information on the KeyWedge interface can be found by clicking here.

Special features

Some keys such as the Function Keys have no direct ASCII equivalent but The Mule can handle it. A special feature built into The Mule allows it to emulate any single or multiple key combination by sending it a special sequence of characters. The Mule can emulate any and every possible key combination you can think of.

The Mule operates by stealing current from the keyboard circuit. Internal links allow this current to be used by the external RS232 device. If the computer cannot supply sufficient power, provision is made for an external power unit. The Mule has an indicator lamp to show when the computer needs help from an external PSU.


The Mule enables any RS232 ASCII device to send data directly into any computer program in real time. Something hitherto impossible. Although it was originally developed for use with barcode scanners, its use in other areas is now widespread. The Mule cuts through all the usual PC to RS232 interface problems...

  • First: You don't need the PC's RS232 serial port. The problems associated with the PC serial port have already been outlined above. In any case you may not have a free port available. The Mule has its own RS232 serial port which has been specially designed to be as simple to use as possible - you can forget the PCs serial port problems!
  • Second: data from your serial device is sent to the PC just as if it were being typed at the keyboard. This means your application can handle the data- even if the Applications Program authors made no provision for input from your serial device.
  • Third: The mule is easy to install and is intuitive in its approach. You do not need any technical knowledge, you do not need software drivers and you do not even need to open the computer case.

Typical applications

The Mule is designed to work with barcode scanners and all other similar devices outputting relatively small bursts of RS232 data. If you are unsure or need advice on your application contact Technical Support

  • Barcode scanners, Tagging readers, and similar devices.
  • Portable data collector downloading.
  • Security: Computer operation without a keyboard.
  • Special interfacing techniques.
  • Multiple data entry or keying points.
  • Remote data collection.
  • Remote control.
Mule Playing Card Logo


  • Size: 95mm x 67mm x 30mm. (about the same as a deck of cards)
  • Weight: 200gms.
  • Computers: All Industry Standard PC`s.
  • Keyboard: Regular 6 pin mini-DIN PS2 style.
  • Industry standard PC/Mac/Unix USB port with HID driver.
  • RS232 Connector & pinout: 9 pin Dee. Same pinout as regular PC.
  • Tough metal casing. Conforms to all known world EMC regulations.
  • RoHS Compliant - lead free.
  • Simple to use but includes full technical support for challenging applications - support for life.


The Mule and KeyWedge are trademarks of Altek Instruments Ltd
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