30 Computer Service and Repair
Be sure you know the location of all fire
extinguishers in your classroom and lab area.
Also, know the fire exit procedure and the
designated area where the class will regroup.
Chemical Safety
As a computer technician, you will come in
contact with hazardous materials to some extent,
for example, toner used in the laser printers. A
Material Safety Data Sheet (MSDS) is required
by federal law for such hazardous materials.
An MSDS provides information such as proper
handling, storage, and disposal of the material.
It also contains information about health effects
or harmful effects from breathing and contact
with the skin or eyes. Material Safety Data Sheets
are meant to be used by emergency response
personnel, such as firefighters and emergency
medical technicians, and workers who commonly
come in contact with the chemicals.
Electronic devices often contain material
considered harmful to the environment. The
Environmental Protection Agency (EPA) provides
information about how to properly dispose of
and recycle electronic equipment. Cities, counties,
and states often have regulations that exceed the
federal government concerning the disposal of
computer and electronic equipment. Always check
the local regulations on proper disposal. The EPA
website has a link to the current state regulations.
An electronic device that causes the most
concern is the CRT. The CRT is a legacy-style
computer or television monitor. It contains
sufficient quantities of lead to warrant it as
hazardous material. Local authorities typically
require CRTs to be recycled and do not allow the
CRT to be handled as normal garbage. It is usually
required that the CRT be recycled or disposed of
by a local agency for a small fee. Not many states
have regulations about how to properly dispose of
CRTs, and there is no one universal regulation.
Other potentially hazardous computer-related
materials are LCD monitors, batteries, and printer
toner. The hazards for these devices are discussed
in detail later in the textbook.
Chapter Summary
• Computers are used in every aspect of daily life and in all industries.
• An analog system uses varying voltage levels, whereas a digital system uses
only two voltage levels.
• Data can be text, graphics, and sounds.
• The binary system consists of only two numbers: 0 and 1; whereas, the
hexadecimal system has sixteen characters: 0–9 and A–F.
• A bit consists of a single 0 or 1, a byte consists of eight bits, and a word is the
total amount of bytes a computer can process at one time.
• Serial data transfer sends one bit at a time in successive order, whereas
parallel data transfer sends more than one bit at the same time.
• Computer speed is usually expressed in bits, whereas storage space is usually
expressed in bytes.
• Some common external connections on a typical PC are video (VGA, DVI,
HDMI), PS/2, USB, FireWire, RJ-45, and audio.
• Some common internal components in a typical PC are CPU, cooling fan,
motherboard, RAM, power supply, hard drive, expansion cards, and cables.
• When a command in a software program is initiated, the operating system
interprets the command and translates it into a set of instructions that the
firmware can interpret, and then control is returned to the software program.
Chapter Summary