CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [31]
Second, many USB devices get their electrical power through the USB connection, so they don’t need batteries or a plug for an electrical outlet. You can even recharge some devices, such as cellular phones, by plugging them into a USB port (Figure 3-13).
Figure 3-13 Cell phone charging via a USB connection
FireWire Connectors
FireWire, also known as IEEE 1394, moves data at incredibly high speeds, making it the perfect connection for highly specialized applications such as streaming video from a digital video camera onto a hard drive. FireWire consists of a special 6-wire connector, as shown in Figure 3-14 or a 9-wire connector for devices that need more speed and power. A smaller, 4-pin version is usually seen on peripherals. Like USB, FireWire devices are hot-swappable.
DB Connectors
Over the years, DB connectors have been used for almost any type of peripheral you can think of, with the exception of keyboards. They have a slight D shape, which allows only one proper way to insert a plug into the socket and makes it easier to remember what they’re called. Technically, they’re known as D-sub or D-subminiature connectors, but most techs call them DBs.
Figure 3-14 FireWire connector and port
Each male DB plug has a group of small pins that connect to DB ports. Female DB plugs connect to male DB ports on the system unit. DB connectors in the PC world can have from 9 to 37 pins or sockets, although you rarely see a DB connector with more than 25 pins or sockets. Figure 3-15 shows an example. DB-type connectors are some of the oldest and most common connectors used in the back of PCs.
Figure 3-15 DB-25 connector and port
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NOTE Each size D-sub connector—called the shell size—has a specific name in the D-sub manufacturing world. A two-row, 9-pin connector, for example, is officially a DE-9 connector rather than a DB-9. The E refers to the 9-pin shell size. Why all of the DA, DB, DC, DD, and DE connectors became DB-x in the world of personal computers is a mystery, but most techs simply call them DB connectors.
It wasn’t that long ago that a typical PC used at least three or more different DB connectors. Over the past few years, the PC world has moved away from DB connectors. A typical modern system has only one or two, usually for video.
RJ Connectors
You have more than likely seen an RJ connector, whether or not you knew it by that name. The little plastic plug used to connect your telephone cord to the jack (techs don’t use the word “port” to describe RJ connectors) is a classic example of an RJ plug. Modern PCs use only two types of RJ jacks: the RJ-11 and the RJ-45. The phone jack is an RJ-11. It is used almost exclusively for modems. The slightly wider RJ-45 jack is used for your network connection. Figure 3-16 shows an RJ-11 jack (top) and an RJ-45 jack (bottom).
Figure 3-16 RJ-11 (top) and RJ-45 (bottom)
Audio Connectors
Speakers and microphones connect to audio jacks on the system unit. The most common type of sound connector in popular use is the 1/8-inch connector, also called a mini-audio connector. These small connectors have been around for years; they’re just like the plug you use to insert headphones into a radio, music player, or similar device (Figure 3-17). Traditionally, you’d find the audio jacks on the back of the PC, but many newer models sport front audio connections as well.
Figure 3-17 Mini-audio jacks and plug
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NOTE Keep in mind that the variety of connectors is virtually endless. The preceding types of connectors cover the vast majority, but many others exist in the PC world. No law or standard requires device makers to use a particular connector, especially if they have no interest in making that device interchangeable with similar devices from other manufacturers.
Devices and Their Connectors
Now that you have a sense of the connectors, let’s turn to the devices common to almost every PC to