Printer problems, Part II

October 26, 1998|By Mike Himowitz

When I wrote a piece about printer problems a couple of weeks ago, I didn't realize I was opening a floodgate. Tales of woe piled in from readers, neighbors, friends and colleagues who had trouble getting their printers to work.

Many of these cries for help came from folks who were trying to gang up a printer, scanner, Zip drive and other gadgets on a single parallel port. I wish I could solve all of these problems - in fact, I wish I could solve all of my own printer hassles. But I can offer a couple of suggestions.

First, a word about how printers communicate with your computer. When you transfer information from your PC to any other device, it's organized into bytes of data. A byte is the amount of information it takes to identify a single typewritten character, and each byte consists of eight binary ones and zeros, known as bits. These bits are converted to alternating voltages that pass over some kind of wiring system. (Don't worry, this is as geeky as we're going to get here.)

PCs have traditionally had two types of ports for transmitting this data. The serial port, designed for modems but commonly used for digital cameras and hookups with hand-held computers, employs two wires to transmit the ones and zeros - one wire in each direction. It's relatively slow, but reliable over long distances.

The parallel port used by printers provides a separate wire for each bit, so that the impulses can march eight abreast on the way to their destination. It's a lot faster than a serial port, but not always reliable at distances greater than 15 feet. Since since most printers are near their host PCs, this isn't a big issue.

Although parallel ports were originally designed for communication that was largely one-way, they can pass information back to your computer. On newer PCs, this two-way communication has been speeded up and enhanced. As a result, today's intelligent printers can tell your computer how a job is progressing, whether there's a paper jam, and how much ink is left in your cartridge.

Over the last five or six years, manufacturers of scanners, video cameras, tape backups and high-capacity, removable disk drives (such as the ubiquitous Zip) have taken advantage of this capability, too. They've designed their gadgets to hook up to your parallel port, so you don't have to open your PC and install a controller for each device.

Most of these devices have a pass-through that allows you to share the parallel port with your printer. Typically, you plug a Zip drive or scanner into your computer and plug the printer into a port on the scanner or Zip, a scheme known as "daisy chaining."

Unfortunately, it doesn't always work. Some sophisticated printers don't like having a Zip drive or scanner between their innards and your PC. The software drivers that control these devices sometimes get confused and hang up when they sense two gadgets hooked up where they expect only one. And if you try to gang up three devices on a parallel port - a printer, scanner and Zip drive, for example - you're almost always looking for trouble.

What can you do when you run into conflicts? First, make sure you have the latest software drivers installed for each device. The software that ships with new models is often buggy, and you can usually find the latest version posted on the manufacturer's Web site.

If that doesn't work, you may want to install a second parallel port in your computer. This isn't rocket science, but you'll have to buy a controller card for $25 to $75, open the case of your PC, and insert it in a free expansion slot. You can hook the printer to the new port and use the original parallel port for your scanner or Zip drive. Just make sure you have an expansion slot available before you go to all this trouble.

Unfortunately, if you have a lot of gadgets hooked to your PC, a new parallel port may cause conflicts of its own. So you'll have to look elsewhere.

A simple, if inelegant, solution for a conflict is an A-B switch. This is a little box, available for $15 to $25, that lets you hook up two devices to the same port and select one or the other with a rotary dial.

It would be nice if all you had to do to switch from a scanner to a Zip drive or printer is flick the switch from device A to B, but Windows 95 and Windows 98 may not allow this because they scan your system for devices they expect to find at startup. If the device isn't there, Windows may not recognize it at all when you switch to it. Also, some printer drivers won't load properly if the A-B switch doesn't point to the printer when you turn the computer on.

As a result, you may have to re-start your computer when you switch devices, but since most people don't use a scanner or Zip drive all the time, it's not an overwhelming inconvenience.

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