Recently my CanoScan N340P scanner has refused to function. When attempting to use the scanner, a message appears advising ‘Unable to open TWAIN source’. I have checked all the connections and have uninstalled and reinstalled to no avail. What is a TWAIN and how do I find one? The computer is running Windows 98 SE.

TWAIN is a program which sits between an application and a scanner, allowing images to be directly scanned into that application (e.g. an image manipulation program such as Photoshop) without the need to run a specialised program to scan the image. Basically, it provides scanners with a standard interface to software packages. Firstly, we should make sure your scanner has the most current TWAIN drivers (version 3.8.2) and also the most current application software (version 2.2.3). These can both be downloaded from www.canon.com.au/products/scanners/scanners_low_medium_volume/CanoScanN340P_drivers.html. Make sure that you uninstall any current scanner drivers and software before installing these updated versions. If the problem continues, we should check that the parallel port on your computer is set to the correct mode. Canon scanners generally require the parallel port be set to EPP (Enhanced Parallel Port) mode. We will need to check this setting in the BIOS setup. Be very careful in the BIOS setup, as unnecessarily changing settings could have serious consequences for your computer - do so at your own risk. Restart your computer and enter the BIOS setup, usually by pressing a specified key when a message like ‘Press DEL to enter setup’ appears during the power-on self-test. You will need to find the page which contains your parallel port mode setting (this is usually on the ‘Integrated Peripherals’ page). Once you have found the setting, write down the current value and then change it to ‘EPP’ (if not already on this setting). Quit the BIOS setup and save changes, then check whether the problem persists. If so, it’s good practice to go back into the BIOS and change the port setting back to its original value.

Should you continue to have problems and if you have a parallel port printer connected to your scanner, then try disconnecting your printer from the scanner, so you only have the scanner connected to the computer. Restart the computer and check whether the problem continues. If not, the reason you cannot use the scanner when the printer is connected is probably because the printer is using the connection and is not allowing the scanner to use the connection. In this situation, it is possible that your printer requires a dedicated parallel port and will not work with a scanner. This problem may have only surfaced recently because you did something like upgrading your printer drivers, which installed an extra feature causing this behaviour. In this case, your alternative is to use a USB cable to connect your printer to your computer (if your printer supports USB), or alternatively buy a new printer which uses USB (since printers are quite cheap).