The A+ Certification & PC Repair Handbook (Charles River Media Networking/Security)
There are three main types of connectors used for keyboards and mice: the 5-pin Deutsche Industrie Norm (DIN) connector, the 6-pin mini-DIN (PS/2) connector, and USB mouse and keyboard connectors. Modern ATX form factor motherboards use PS/2 connectors for both the mouse and the keyboard. Older AT systems typically used a 5-pin DIN connector for the keyboard and a serial mouse. Figure 21.4 shows a 5-pin DIN and a 6-pin mini DIN (PS/2) connector.
The 5-pin DIN keyboard connector was used in AT- and XT-class computers for a keyboard connection. It is much larger than a 6-pin mini-DIN connector and requires its own 5-pin port. The more popular 6-pin mini-DIN, otherwise known as a PS/2 connector, is the standard connector in use today for mice and keyboards. Nearly all systems today support PS/2 connections for mice and keyboards. (See Figure 21.1 for PS/2 mouse and keyboard ports on the back of a system using the ATX form factor.)
Newer systems support USB mice and keyboard connections, which are very easy to install, support, and use. USB connectors will be discussed shortly.
Older systems use a serial port DB-9 connector for what is commonly referred to as a bus mouse. A bus mouse requires the use of a free COM port and IRQ.
Following are some very important facts to remember about mice and keyboards for the Core exam. The most important feature to look for when replacing a mouse or keyboard is the connectors associated with the device.
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A PS/2 mouse and an ATX-style keyboard connector look identical. It is easy to make the mistake of plugging the keyboard connector into the mouse port, or vice versa.
Note You should only connect a PS/2 mouse or keyboard to a system unit if the system is powered off. If the system is on when you make a keyboard or mouse swap, it is possible that the mouse or keyboard may not be recognized.
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USB mice and keyboards can be replaced, or ‘hot-swapped’ while a system is running.
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