Page 52 - Asterisk™: The Future of Telephony

will cut down on the occurrence of ground loops, which can cause anything from
buzzing and humming noises to damaged or destroyed equipment.

Electrical Circuits
If you’ve ever seen the lights dim when an electrical appliance kicks in, you’ve seen the
effect that a high-energy device can have on an electrical circuit. If you were to look at
the effects of a multitude of such devices, each drawing power in its own way, you
would see that the harmonically perfect 50 or 60 Hz sine wave you may think you’re
getting with your power is anything but. Harmonic noise is extremely common on
electrical circuits , and it can wreak havoc on sensitive electronic equipment. For a PBX,
these problems can manifest as audio problems, logic errors, and system instability.
Ideally, you should never install a server on an electrical circuit that is shared with other
devices. There should be only one outlet on the circuit, and you should connect only
your telephone system (and associated peripherals) to it. The wire (including the
ground) should be run unbroken directly back to the electrical panel. The grounding
conductor should be insulated and isolated. There are far too many stories of photo-
copiers, air conditioners, and vacuum cleaners wreaking havoc with sensitive electron-
ics to ignore this rule of thumb.

The electrical regulations in your area must always take precedence over
any ideas presented here. If in doubt, consult a power quality expert in
your area on how to ensure that you adhere to electrical regulations.
Remember, electrical regulations take into account the fact that human
safety is far more important than the safety of the equipment.

The Equipment Room

Environmental conditions can wreak havoc on systems, and yet it is quite common to
see critical systems deployed with little or no attention given to these matters. When
the system is installed, everything works well, but after as little as six months, compo-
nents begin to fail. Talk to anyone with experience in maintaining servers and systems,
and it becomes obvious that attention to environmental factors can play a significant
role in the stability and reliability of systems.

Humidity
Simply put, humidity is water in the air. Water is a disaster for electronics for two main
reasons: 1) water is a catalyst for corrosion, and 2) water is conductive enough that it

‖ On a hobby system, this is probably too much to ask, but if you are planning on using Asterisk for anything
important, at least be sure to give it a fighting chance; don’t put anything like air conditioners, photocopiers,
laser printers, or motors on the same circuit. The strain such items place on your power supply will shorten
its life expectancy.

24 | Chapter 2: Preparing a System for Asterisk