Parallel Port Complete- P2: From its origin as a simple printer interface, the personal computer's parallel port has evolved into a place to plug in just about anything you might want to hook to a computer. The parallel port is popular because it's versatile-you can use it for output, input, or bidirectional links-and because it's available-every PC has one. | Chapter 1 Figure 1-2 The photo on the left shows the back panel of an expansion card with a parallel port s 25-pin female D-sub connector on the left side of the panel. The other connector is for a video monitor. The photo on the right shows the 36-pin female Centronics connector used on most printers. fer information between the parallel port and the CPU memory andothersystem components. Connectors The PC s back panel has the connector for plugging in a cable to a printerorother device with a parallel-port interface. Most parallel ports use the25-contactD-sub connector shown in Figure 1-2. The shell the enclosure that surrounds the contacts is roughly in the shape of an upper-case D. Othernames forthisconnector are the subminiature D DB25 D-shell or just D connector. The IEEE 1284 standard for the parallel port calls it the IEEE 1284-A connector. Newer parallel ports may use the new compact 36-contactIEEE1284-C connector described in Chapter 6. The connector on the computer is female where the individual contacts are sockets or receptacles. The cable has a mating male connector whose contactsare pins or plugs. The parallel-port connector is usually the only female 25-pin D-sub on the back panel so there should be little confusion with other connectors. Some serial ports use a 25-contact D-sub but with few exceptions a 25-pin serial D-sub onaPCis male with the female connector on the cable-the re verseof theparall cl - port convention. Other serial ports use 9-pin D-subs instead. SCSI is another interface whose connector might occasionally be confused with the parallel port s. The SCSI interface used by disk drives scanners andother devices usually has a 50-contact connector but some SCSI devices use a25-con-tact D-sub that is identical to the parallel-port s connector. If you re unsure about which is the parallel-port connector check yoursystem documentation. When all else fails opening up the enclosure and tracing t he cable from the connector to an expansion .
