Hardware Reference
In-Depth Information
Underwriters Laboratories has produced an excellent standard that governs surge suppressors, called
UL 1449. Any surge suppressor that meets this standard is a good one and definitely offers a line of
protection beyond what the power supply in your PC already offers. The only types of surge
suppressors worth buying, therefore, should have two features:
• Conformance to the UL 1449 standard
• A status light indicating when the MOVs are blown
Units that meet the UL 1449 specification say so on the packaging or directly on the unit. If this
standard is not mentioned, it does not conform. Therefore, you should avoid it.
Another good feature to have in a surge suppressor is a built-in circuit breaker that can be manually
reset rather than a fuse. The breaker protects your system if it or a peripheral develops a short.
Network and Phone Line Surge Protectors
A far bigger problem than powerline surges is surges through network or phone cabling. I've
personally experienced surges resulting from nearby lightning strikes damage multiple computers and
other equipment via Ethernet and telephone lines, while virtually nothing was damaged through the
power lines. In systems with separate network cards, the damage was often limited to just the card,
while in systems with the network interface built in to the motherboard, the motherboard itself was
damaged. In many areas, the cable and phone lines are above ground, making them especially
susceptible to lightning strikes.
Several companies manufacture or sell simple surge protectors that plug in between your modem and
the network or phone lines. These inexpensive devices can be purchased from most electronics
supply houses. Some of the standard power line surge protectors include connectors for network or
phone line protection as well.
Line Conditioners
In addition to high-voltage and current conditions, other problems can occur with incoming power.
The voltage might dip below the level needed to run the system, resulting in a brownout. Forms of
electrical noise other than simple voltage surges or spikes might travel through the power line, such
as radio-frequency interference or electrical noise caused by motors or other inductive loads.
Remember two things when you wire together digital devices (such as computers and their
peripherals):
• Any wire can act as an antenna and have voltage induced in it by nearby electromagnetic fields,
which can come from other wires, telephones, CRTs, motors, fluorescent fixtures, static
discharge, and, of course, radio transmitters.
• Digital circuitry responds with surprising efficiency to noise of even a volt or two, making
those induced voltages particularly troublesome. The electrical wiring in your building can act
as an antenna, picking up all kinds of noise and disturbances.
A line conditioner can handle many of these types of problems. It filters the power, bridges
brownouts, suppresses high-voltage and current conditions, and generally acts as a buffer between the
power line and the system. A line conditioner does the job of a surge suppressor, and much more. It is
more of an active device, functioning continuously, rather than a passive device that activates only
when a surge is present. A line conditioner provides true power conditioning and can handle myriad
problems. It contains transformers, capacitors, and other circuitry that can temporarily bridge a
