System information

One of the benefits of clean power is a reduction in heat, which means less stress on
components, leading to a longer life expectancy.
Properly grounded, conditioned power feeding a premium-quality power supply will
ensure a clean logic ground (a.k.a. 0-volt) reference
‡
for the system and keep electrical
noise on the motherboard to a minimum. These are industry-standard best practices
for this type of equipment, which should not be neglected. A relatively simple way to
achieve this is through the use of a power-conditioned UPS.
§
Power-conditioned UPSs
The UPS is well known for its role as a battery backup, but the power-conditioning
benefits that high-end UPS units also provide are less well understood.
Power conditioning can provide a valuable level of protection from the electrical envi-
ronment by regenerating clean power through an isolation transformer. A quality
power conditioner in your UPS will eliminate most electrical noise from the power feed
and help to ensure a rock-steady supply of power to your system.
Unfortunately, not all UPS units are created equal; many of the less expensive units do
not provide clean power. What’s worse, manufacturers of these devices will often
promise all kinds of protection from surges, spikes, overvoltages, and transients. While
such devices may protect your system from getting fried in an electrical storm, they will
not clean up the power being fed to your system, and thus will do nothing to contribute
to stability.
Make sure your UPS is power conditioned. If it doesn’t say exactly that, it isn’t.
Grounding
Voltage is defined as the difference in electrical potential between two points. When
considering a ground (which is basically nothing more than an electrical path to earth),
the common assumption is that it represents 0 volts. But if we do not define that 0V in
relation to something, we are in danger of assuming things that may not be so. If you
measure the voltage between two grounding references, you’ll often find that there is
a voltage potential between them. This voltage potential between grounding points can
be significant enough to cause logic errors—or even damage—in a system where more
than one path to ground is present.
‡ In electronic devices, a binary zero (0) is generally related to a 0-volt signal, while a binary one (1) can be
represented by many different voltages (commonly between 2.5 and 5 volts). The grounding reference that
the system will consider 0 volts is often referred to as the logic ground. A poorly grounded system might have
electrical potential on the logic ground to such a degree that the electronics mistake a binary zero for a binary
one. This can wreak havoc with the system’s ability to process instructions.
§ It is a common misconception that all UPSs provide clean power. This is not at all true.
650 | Appendix C: Preparing a System for Asterisk