Installing an HP ScanJet under Windows NT

Scanners are important hardware items for many Windows NT sites, but getting a scanner to work under NT can be a challenge. To do so, you need an NT-compatible scanner, a SCSI host adapter, and the right drivers. After several tries, I finally got my Hewlett-Packard (HP) ScanJet desktop scanner up and running under Windows NT 3.51 and 4.0 (for more information about my hardware setup, see "Author's System Configuration," page 137). Here, I explain the procedure I used to install my scanner and provide tips you can apply to running flatbed scanners (or other types of image scanners) in your NT shop.

Windows NT Compatibility
Flatbed scanners are scanners that have a flat glass surface on which you place the object you want scanned. A reading head moves across the surface to input information.

Currently, HP ScanJet scanners are the only flatbed scanners that Microsoft officially supports (i.e., includes on the Hardware Compatibility List--HCL) for Windows NT versions 3.51 and 4.0. However, several other flatbed scanners run under NT 3.51 or 4.0, including Epson, Microtek, Xerox, and UMAX scanners. According to users of these scanners, the manufacturers have developed the appropriate drivers, making their installation under NT 3.51 and NT 4.0 fairly straightforward.

SCSI Interface
To attach a scanner to an NT system, you first need a cable and a SCSI interface, or host adapter. (You can't use a parallel port with NT. For explanations of SCSI and other terms in this article, see "Glossary," page 134.) Although some motherboards include a built-in SCSI bus, most SCSI interfaces take the form of a card that you insert into a spare expansion slot. Microsoft has certified more than 100 SCSI adapters as compatible with NT 3.51 and 4.0, among them are products from Adaptec, BusLogic, and NCR. Again, check the HCL for a complete list of supported SCSI adapters.

The Right Drivers
A driver is a program that controls a piece of hardware and lets it exchange data with other hardware and software. A SCSI scanner usually needs two drivers to work, or more likely, two sets of modular drivers and their associated DLLs and system files. The host adapter driver is often called the system-level driver; the scanner driver is usually called the source driver. Make sure you have the latest versions of all required drivers.

Driver compatibility is a problem in the NT environment. For example, the host adapter needs the correct driver to communicate with NT, the scanner needs a driver to talk to the host adapter and to NT, and the drivers must work together. In NT 3.51 and 4.0, Microsoft provides two HP ScanJet scanner drivers similar to the original HP drivers. (Microsoft's developers customized the original drivers for NT.) You'll want to use these Microsoft drivers, rather than the original HP drivers, to ensure that your HP ScanJet scanner works hand in hand with NT.

To further complicate matters, scanner application programs often have modules to communicate with the scanner via the operating system and the host adapter. Two main industry standards exist for image and scanner interfaces: Image and Scanner Industry Standard (ISIS) and TWAIN. Many software developers and scanner manufacturers have designed their application software, scanners, and drivers to comply with one or both standards. TWAIN is more common than ISIS for scanning products that work with NT. ISIS is more commonly used for optical character recognition (OCR) packages. For example, Adobe's Photoshop and Pictronics' IntelliScan (an image-scanning and editing package) are TWAIN compliant. Pictronics claims its product supports all desktop scanners through the TWAIN interface on NT. Be aware, however, that not all TWAIN software works with NT; as mentioned earlier, you need the latest drivers. For example only TWAIN 1.6-compliant programs, which include TWAIN_32 drivers (not the older TWAIN32 modules), work with NT 3.51 and 4.0. Thus, Adobe Photoshop 3.0.5, which uses the TWAIN_32 drivers, works with NT; however, version 3.0 doesn't work because it uses the TWAIN32 drivers.