The only connector available on the majority of contemporary personal printers for connecting to computers is the USB port. However, many heavy-duty corporate printers come with additional port choices for tethering to older workstations, networks, and servers. Parallel ports emerged as the most widely used printer interface among the different printer interfaces developed throughout the years. Parallel cables were the preeminent type of connection medium for printers up until the advent of USB. They were first introduced in the early 1970s by Centronics and later modified for use with personal computers by IBM in the 1980s. Even though USB is widely used, many printers are still designed to work with different kinds of parallel cords.
Connector Types
Computer parallel printer ports are essentially all the same, with the exception of a very small number of specialised equipment. As a result, no matter the type, the ends of the parallel cables connecting to PCs are the same. All parallel cables include a male DB-25 connector that attaches to the computer’s back panel’s female DB-25 port. However, the sort of external device to which a parallel cable connects can affect the connectors on the other end of the connection. Before USB became widely used, 36-pin Centronics adapters were used in the majority of printers. This kind of interface is also typically found in contemporary heavy-duty business printers that still feature parallel port connections. Therefore, a male DB-25 to Centronics 36-pin connection type is the most typical connector configuration seen on a parallel cable. A smaller Mini-Centronics connector was included with a few vintage HP and IBM laser printers. A big female slot opening with metal slots on either side is present on the typical 36-pin Centronics connector used to connect to printers. The Mini-Centronics interface resembles a much smaller version of the original Centronics connector and is used for cables required for a few outdated laser printers.
IEEE Standards
Manufacturers create parallel cables based on IEEE industry standards, just like they do with the majority of other computer cables and gadgets. The numerous printer cables and the methods by which they communicate data from computers to printers or other devices are defined by the IEEE 1284 standards. IEEE 1284-I and IEEE 1284-II are the two different parallel cable specifications that are available. Cables that connect DB-25 to Centronics 36-pin cables are covered by IEEE 1284-I. All cables that contain a Mini-Centronics connection are covered by IEEE 1284-II. Therefore, seek for a printer that supports the IEEE 1284-I standard unless you already own an old HP or IBM printer with a Mini-Centronics connector. Both IEEE standards for parallel cables use wire assignments and pinouts that are essentially identical. Daisy chaining up to eight devices from a single DB-25 parallel port on a computer is also supported by both 1284-I and 1284-II. The computer operating system and the application from which you print must both be able to recognise various devices sharing a single port in order to use the daisy chain capability with parallel ports. Parallel ports are supported by current Windows versions for port sharing. However, the feature isn’t supported by many apps.
Parallel Port Modes
Multiple means of communication between the host computer and a printer or other device are supported via parallel wires. Early parallel cables only supported the Centronics standard mode, often known as Compatibility mode or SPP (Standard Parallel Port) mode. Since the early 1990s, parallel cables have supported both EPP (Enhanced Parallel Port) and ECP (Extended Capabilities Port) modes, which comply with IEEE 1284 standards. While EPP and ECP support transfer speeds of 2 megabytes per second and roughly 5 megabytes per second, respectively, SPP supports transfer speeds of up to about 480 kb per second. Full-duplex mode (sending and receiving data of the same type) is supported by SPP, EPP, and ECP if the programme initiating print jobs uses commands connected to Nibble Mode. The computer sends 4 bits of data to the associated printer when starting a print job in Nibble mode, then waits a brief amount of time for a response. The data is sent in full-duplex mode, resulting in speedier printing and the release of the port by the application, if the computer receives the printer’s response within a certain wait period. If the printer does not respond quickly, the computer switches to Compatibility mode and delivers data in half-duplex mode, which often takes longer to finish print jobs.
Adapter Cables
There are various adapter cables available in addition to typical parallel cable types for connecting PCs with parallel ports to older printers with serial output as well as PCs without parallel ports. Business customers can typically connect line or receipt printers to a computer’s parallel port without the need for a dip-switch or conversion box by using a parallel-to-serial adapter cable. Business owners can connect and use outdated printers with USB-to-parallel converter cables for newer workstations lacking parallel connections. There is presently no dependable parallel-port to USB printer cable, thus if you want to connect a USB printer to an older computer with only a parallel port, you must utilize an active conversion box.