Centronics parallel interface
The original Centronics parallel interface became an industry
standard in 1981 when IBM introduced the PC. The parallel port on these PCs
transferred data at around 150-KBps. At that time, a fast peripheral was a
240-character-per-second dot-matrix printer. Today, you are more likely to be
connected to an 8-page-per-minute (or faster) laser printer, or an ink-jet
printing 1 or 2 megabyte color graphics files. Complex graphics and faster
printers have facilitated the need for a higher speed interface capable of
transferring data to the printer at much higher rates than the capabilities of
the original Centronics parallel interface.
Distance
Not only was the original Centronics parallel interface slow,
it was also notorious for having problems printing at distances of more than 10
or 15 feet. Attempting to print to a printer at anything over 10 of 15 feet was
"potluck", commonly resulting in characters being changed or dropped,
complete garbage or sometimes nothing at all coming out of the printer.
IEEE 1284 Standard
The IEEE 1284 standard defines a high speed interface
designed to work at 30 feet (10 meters). In some cases IEEE 1284 parallel ports
are running 100 to 200 times faster than the original Centronics-style parallel
ports! In addition to higher speed and longer distances, the IEEE 1284 standard
also defines bi-directional communication through the parallel port, allowing
the printer to not only receive data, but also to talk back to the PC.
In early 1995, printer manufacturers (such as
Hewlett-Packard, Lexmark and Canon to name a few) began shipping most (if not
all) of their printer models with parallel interfaces designed around the IEEE
1284 standard. These printers ship with software drivers that take full
advantage of the high speed data rates and bi-directional capability of the IEEE
1284 standard. With these software drivers and the bi-directional capability of
the IEEE 1284 standard, the printers can signal back to the PC if they are out
of paper, need toner (or ink), have a paper jam or have some other problem or
malfunction.
The need for IEEE 1284 cables and
switchboxes
This brings us to the most common question concerning the IEEE 1284 standard and printers using this interface: why do I
need a different parallel printer cable or switchbox for my new printer than the
one I used with my old printer? The reason is simple: you can't transfer data at
these higher speeds and support the bi-directional communication through
parallel printer cables that were designed for the original, slower Centronics
interface. Remember the 15' distance problem mentioned earlier? Imagine the type
of printing problems that could possibly occur when attempting to push data
through an old style parallel cable at 100 to 200 times the speed! This is why
the majority of the printer manufacturers recommend using an IEEE 1284 Compliant
Printer Cable with their new printers.
IEEE 1284 compliant products
The IEEE 1284 cables sold by CWOL.COM are designed and built to be
fully compliant with the IEEE 1284 standard. The cables are made with top
quality twisted pair conductors (each signal pair is twisted up to 36 turns per
meter) that match the impedance of the IEEE 1284 interface. The twisted pair
conductors are shielded with a minimum of 85% optical braid coverage over a foil
shield. Only cables built to these exacting standards can ensure the data
integrity and high data rates that are possible with the IEEE 1284 standard. The
IEEE 1284 switchboxes we carry support both the higher speeds utilized by the
IEEE 1284 standard and it's bi-directional communication capability, allowing
you to take full advantage of the features of bi-directional printers as well as
other devices having the IEEE 1284 interface like scanners, zip drives, CD-ROM
drives etc. |
