As basic an issue as power might seem, it should be your starting point when you have a device that is not functioning correctly. For example, you might get up one morning and find that although your computer is working just fine, nothing prints. You check the printer and find that it's turned on and has paper loaded; you just can't figure out what the problem might be. Check your hub or switch. Has someone
unplugged the AC adapter that powers the device? Most hubs have a power LED that indicates when the unit is
up. If you have a power strip, check that too. It's easy,
in a small office where you don't route cables through the wall, for something as simple as an unplugged device to cause problems. Of course, look to see that no one has switched the power strip to the off position.
can refer to either a temporary switched power strip or to a true surge protector (also known as a surge
). At a minimum, a
voltage surges from
connected equipment. Some also filter out electrical noise and interference.
You should use
surge suppressors to protect your SOHO network and other electronics around your home. A true surge suppressor is a UL 1449rated device (check the packaging for the UL rating). Any surge suppressor that meets this standard is a very good one and 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 at least two features:
Conformance to the UL 1449 standard
A status light indicating when the unit can no longer provide protection. It's preferable to look for units that shut down power to the outlets to prevent devices from being damaged when the unit can no longer stop surges.
Other useful features to look for include
Increased spacing for AC/DC converters
Many peripherals, such as broadband and dialup modems and some types of printers, are powered by AC/DC converters (also known as power blocks or briquettes). Surge suppressors that provide extra spacing between outlets enable all outlets to be used, even when some are occupied by power blocks. When combined with a double-side design (in which both sides of a surge suppressor include outlets), wide spacing of AC outlets helps assure that every outlet is a usable outlet.
Surge suppression for data lines
If you have a dial-up modem, an all-in-one device, or a fax machine connected to a phone line, don't overlook the possibility of phone line surges. Phone lines carry power (enabling the phone to be used during a power
), so they can also transmit a damaging surge to the modem or the server. Surge protectors with RJ-11 ports provide protection against phone line surges. A few surge protectors on the market now offer surge protection for RJ-45 Ethernet cables as well. Surge suppressors marketed for home theater systems often include surge suppression for RG-6 coaxial cable (used for cable modem, satellite TV, and cable TV).
Built-in circuit breaker
The breaker protects your system if it or a peripheral develops a short.
For greater protection against electrical problems, consider connecting each PC and network device (such as a broadband modem and router) to a battery backup (UPS) device. UPS devices are available from many
and are designed to provide a few minutes of runtime when the power goes outenough time to close applications and shut down computers without losing data. Many UPS units feature signal lights to
you of battery condition and whether your PCs are running on normal AC power or on battery power from the UPS. A single UPS can power a computer, a monitor, and typical external peripherals, such as a cable modem and router. However, printers should not be connected to a UPSthey draw too much power, and are not mission-critical devices.
For more information on UPS devices, see Chapter 5, "Protecting the Network: Preventive Maintenance Techniques."
Finally, if you are having power problems with all the computers on your network, check the fuse box or power panel in your home or office to be sure that the fuse or circuit breaker at that point hasn't disconnected the power.
If computers or other devices on a SOHO network are malfunctioning, don't overlook the possibility that they are connected to poor-quality or incorrectly wired outlets. An inexpensive AC circuit tester such as the one shown in Figure 50.1 can be used to determine if the electrical outlets in your home or office has been configured properly. This tester uses signal lights to
common wiring problems, such as
Figure 50.1. This circuit tester indicates the outlet is wired correctly.
Another type of electrical tester known as a multimeter can be used to test electrical outlets for correct AC voltage levels. A typical shirt-pocket multimeter is shown in Figure 50.2. Multimeters can also measure DC voltage cable continuity and perform other tests. See the multimeter's instruction manual for details and testing
Figure 50.2. A typical multimeter. Use the probes at right for testing outlets and devices.