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Heating, ventilation, and air conditioning (HVAC)
For computer components, design HVAC systems with the following in mind:
- Keep temperature between 70 and 74 degrees to prevent components from overheating.
- Keep humidity between 40 and 70 percent to prevent electrostatic discharge (ESD).
- Make sure server rooms have separate ducting or systems from the rest of the building for better control.
- Use positive pressure systems. Positive pressure systems protect the air quality in the facility by causing air to be forced out through doors, windows, and other openings. Negative pressure systems draw air in, potentially bringing in airborne particles such as dust or smoke. Positive pressure systems are more energy effective.
- For areas with heavy smoke or dust, add filters to air intake systems to filter out airborne particulates.
Interference is a signal that corrupts or destroys regular signals. Interference affects signals used by two devices to communicate on a network. Listed below are two types of interference that affect computer networks.
Electromagnetic Interference (EMI)
Electromagnetic Interference (EMI) is interference that affects wired networking signals.
- EMI is caused by motors, heavy machinery, and fluorescent lights.
- Use shielded twisted pair cable to protect signals sent on Ethernet twisted pair cabling. If necessary, use fiber optic cables to eliminate the effects of interference.
Radio Frequency Interference (RFI)
Radio Frequency Interference (RFI) is interference on the radio channel used by wireless networking devices.
- RFI can be caused by nearby wireless devices using the same channel, cordless phones, or microwave ovens.
- Wireless networks that use the 2.4 GHz frequency range (801.11b and 802.11g) are susceptible to RFI.
RFI can be reduced by using a wireless networking standard that operates in the 5.75 GHz range, or by using a different channel for wireless devices.
Magnetic fields located close to a computer can cause undesired effects or even data loss.
Floppy drives, hard drives, and tape storage devices use magnetic charges on a disk or tape for storing data. While hard disks are shielded and protected from all but the strongest magnets, be careful with floppy disks and tapes. Getting a magnet too close to these components could erase data.
Magnets near a CRT monitor can distort the images on the screen.
- CRT monitors, speakers, motors, and generators contain magnets (keep sensitive components away from these devices).
- Solid state storage devices (such as RAM or flash drives) are not affected by magnetic fields.
Prior to cleaning computer components, power down and unplug components and let them sit for at least 30 minutes to cool.
The following table lists power conditions you should be familiar with.
- Surge - Over voltage that lasts seconds
- Spike - Over voltage that lasts milliseconds
- Sag - Under voltage that lasts milliseconds
- Brownout - Under voltage that lasts seconds (lights dim)
- Blackout- Complete power failure
A surge protector protects against over voltages.
- A power strip provides multiple power outlets from a single plug-in, but is not necessarily a surge protector.
- Surge protectors can be destroyed by surges and lose their ability to protect.
- Consider using a surge protector with an indicator light to show whether it is working correctly.
A line conditioner modifies the power signal to remove noise and create a smooth alternating current (AC) signal.
Standby Power Supply (SPS)
A standby power supply is an offline device that switches over to provide power when an under voltage occurs. If the switchover is not fast enough, the computer loses power.
Uninterruptible Power Supply (UPS)
An uninterruptible power supply is an online device that is constantly providing battery power to the computer and being recharged by the wall outlet.
There are two types of UPS systems:
An online UPS constantly powers the computer from the battery. An offline UPS powers the computer from the wall power. When the power fails, a switch inside the UPS switches to power the computer from the battery. This is the most common form of UPS.
Your organization uses an 802.11b wireless network. What system would create intermittent interference?
Wireless TV distribution system running at 2.4 GHz
What cleaning compound would you need in your cleaning kit?
Alcohol-based monitor wipes
What does a beeping from the UPS mean?
The computer is running on the UPS battery power.
Which of the following devices helps protect against temporary, above-normal voltages?
What are the features should you look for when selecting a vacuum cleaner for your cleaning kit?
- A vacuum cleaner that blows as well as vacuums
- Non-static generating
Besides protecting a computer from under voltages, a typical UPS performs what two actions:
- Protects from over voltages
- Conditions the power signal
What is the most helpful in keeping the computer cool?
Vacuum dust from the system
When you troubleshoot connectivity problem on an Ethernet Network that has intermittent connectivity to the network and UTP patch cable is run 75 feet form the wall outlet, passes though the ceiling and over several florescent light fixtures before reaching the clients system. What could be the problem?
EMI interference from the lights
Cable is ran across the floor and it has wear through and break. Where should you rerun the cable?
You should run the cable through the ceiling area instead of across the floor.
What device should not typically be plugged into a UPS?
Received a new laptop that was shipped and left on front porch on a cold day. What should you do prior to turning it on?
Let the computer warn up before turning it on.
Which of the following statements about cleaning monitors and display devices are true?
You should clean the monitor while it is powered off and the power plug removed to avoid getting a shock.
What is the best way to protect a computer from power spikes during an electrical storm?
Unplug from the AC outlet.
What are the common tools used to physically clean the inside of a computer.
- Compressed air
- Natural bristle brush
What rating type of UPS do you need for each PC in a remote office.