Neon-komputadór

Printers and Scanners

Printers and scanners operate on very similar technologies and concepts. The former provides a hardcopy of a data file - the latter converts a hardcopy into a data file. Both are typically sent to the parallel port of a computer, also known as LPT (line printer), although SCSI and USB printers and scanners do exist. Even resolution is calculated in the same manner.

There are three basic types of printer technology, laser, inkjet and dot matrix. The former creates an electrostatic image on a photosensitive drum and applies toner to sensitized areas, rather like a photocopier. Inkjets use nozzles that spray ink onto the page and dot matrix printers uses press pin heads through an inked ribbon, rather like a typewriter. Of the three technologies, laser printers provide the best resolution and the lowest cost per page, although they have a higher initial cost. They are particularly preferable in a tropical climate like East Timor where temperature and humidity levels can wreck havoc on inkjet printers (except for the new models which use solid-ink technology).

Printer resolution refers to the size and number of dots, usually expressed as dots-per-inch (dpi). In the discussion on monitors, the resolution there is number of dots per screen (such as 640x800), however this usually converts to a mere 50-80 dpi. Contemporary laser printers on the other hand usually have a minimum of 600dpi. Another determinate of quality with laser printers is whether the printer uses interpolation or not. This is an inexpensive means for a printer to physically print at a higher resolution without the requisite memory or processing power via scaling. The output however is by no means as good. Paper quality is also a factor, especially with inkjet printers where anything less than specialist heavy, smooth, fast-drying paper will always produce inferior quality results.

Printers have memory chips and most laser and inkjet printers have processors as well. This memory and processor is very important for laser and inkjet printers as it helps determine the speed of printing, the conversion of the data to a page description language (PDL), how much data can exist in a buffer and so forth. Finally, a very important component of a printer is the driver, the interface between the computer system and the printer. The driver informs the system what capabilities the printer has, what fonts it can use, the type of paper, the PDL and so forth. One can usually print with a similar printer driver however the full range of a printer's capability will not be used.

Network Printer Problems and How to Fix Them

Nearly all the printers in the Ministry of Foreign Affairs and Cooperation are networked - a simple reality from the fact of that we have some fifty system units and only about a dozen printers. Thus, the most common printer error is that a user cannot connect to a networked printer. There are several basic steps one should test before asking a systems administrator or other technician for assistance.

Check whether the printer is actually switched on. Whilst this applies to all peripherals it can often be very easy to overlook. Make sure that the printer is connected to the correct computer. Make sure that the user is attempting to print to the correct printer (go to control panel, printers on MS-Windows98) Users often change the printer that a computer is connected to without putting it back - this upsets the others who depend on that printer via networking. Check whether the user in question has sharing rights to the computer and printer (go to control panel, networking on Windows98).

Finally, make sure that the right printer driver is being used. Because users change the printer that they use so often sometimes they seem to forget which printer they are connected to (go to control panel, printers in Windows98).

As mentioned previously, scanners and printers use fairly similar technological concepts. One converts data into hardcopy and the other converts hardcopy in data. Basically, they are almost exactly the same as a photocopier or the reverse of a laser printer. A light bounces of a document, is reflected to a charge coupled device (CCD) of light-sensitive diodes that convert the light into electricity. The electricity is sent to an Analog to Digital Converter (ADC) that converts the analog electricity to digital pixels that is then sent to the scanner application. Unlike printers, scanners can use interpolation quite effectively. A scanner with 600dpi optical resolution often can reach a maximum resolution of 2,400dpi.