9.3 Connecting a Printer
9.3.1 Serial, parallel, USB, SCSI, and network communication types
Printers require a method of communicating with the computers they serve. Communication is accomplished through the ports on both the printer and the computer (or network device) or by using wireless technologies (such as infrared signals). Most printers use serial, parallel, USB, SCSI, and network cables and ports to receive information from computers.

Serial
Serial ports are usually found on dot matrix printers that do not require high-speed transfers of data. Transmitting information serially involves single characters being transmitted one at a time. Serial ports are D-Shell ports that are categorized as being either male or female and also by the number of pins available for each port. Popular serial cables include 9-pin on both ends, 25-pins on both ends, or a combination of the two. Usually, the ends of the printer cables are secured to the ports on the printer and PC with thumbscrews. The maximum length of serial cable is 50 feet (18m).

Parallel
Printers that use parallel communication have faster data transfer rates than serial printers because parallel data transfer moves multiple bits of information in a single cycle. This provides a wider path for information moving to or from the printer. IEEE 1284 is the current standard for parallel printer cables. Other standards such as Enhanced Parallel Port (EPP) and Enhanced Capabilities Port (ECP) allow bi-directional communication across the parallel cable. Parallel printer cables have two unique ends: a 1284 Type-A 25-pin DB 25 connector and a 36-conductor Centronics connector. The Type-A connector connects to the PC (or daisy-chained peripheral) and has two screws that should be hand-tightened. The Centronics connector connects to the printer and should be secured in place with the port clips. The maximum length for IEEE 1284 cables is 15 feet (3M). 

SCSI
Small Computer System Interface (SCSI) is a type of interface that uses parallel communication technology to achieve high data transfer rates. There are many types of SCSI with the most popular being SCSI 1 (plain SCSI), SCSI 2 (wide SCSI), and SCSI 3 (fast SCSI). SCSI printers and computers require the proper cabling for the ports. These ports can be DB 50 (male or female), MiniDB 50 (male or female), and DB 68 (male or female).

USB
Universal Serial Bus is a very popular communication type for not only printers but also other devices due to its speed and ease of setup. Newer operating systems offer Plug and Play USB support. When a device is added to a computer system via USB, it is automatically detected, and the driver installation process begins. A USB cable is a four-wire cable that also has two unique ends. One end of the USB is the wider, slimmer end that connects to the PC. The other end, which is square, connects to the printer. These ends are keyed so that they can only fit one way into each port.

FireWire
FireWire, also known as i.LINK or IEEE 1394, is a high-speed, platform-independent communication bus. It interconnects digital devices such as digital printers, scanners, digital cameras, hard drives, and so on. Developed by Apple, FireWire was designed to allow peripherals to seamlessly plug into a computer. It also allows a device such as a printer to be hot-plugged. FireWire provides a single plug-and-socket connection on which up to 63 devices can be attached with data transfer speeds up to 400 megabits per second (Mbps). IEEE 1394 implementations are envisioned to replace and consolidate modern serial and parallel interfaces, such as Centronics parallel, RS-232C, and SCSI. The first printers to be introduced with FireWire are just beginning to come on the market.

Network
Network printers are now popular in the workplace because they act as shared resources for all users on the network. Users are not required to have their own printers. These printers offer many options (such as LAN fax, duplex, and finishers) and have high-speed outputs. Connecting a printer to the network requires the correct type of cabling that is compatible with the existing network. Most network printers ship with an RJ-45 interface for connection into an Ethernet network. Other connection options include BNC and Token Ring ports. The maximum length of a Cat 5 cable to connect a printer to the network is 100 meters.

Infrared
Current wireless printing technology is built upon infrared technology. This technology uses a spectrum of light that is invisible to the human eye. For infrared communication to take place between a printer and a computer, transmitters and receivers are required on both devices. When setting up an infrared printer, there must be a clear line of sight between the transmitters and receivers on both devices with a maximum distance of three meters.