Node Zero and Structure Cabling
(or “Why you can never enough Cat5”)
The concept of a Node Zero (N0) stems from the need to terminate the wires that run all over the house at a single central point.
In the long term, this provides a great deal more flexibility, since any two cables can then be spliced or joined, instead of the requirement to lift floorboards and chase walls each time a requirement for a new connection between two points arises.
Node Zero also serves as a convenient point to house other, relatively antisocial, control equipment - such as control PC's and amplifiers which have to run continuously and are best kept out of sight but need to remain accessible.
Cabling
Although you may believe that you have a clear understanding of how cables will be used in the long term, bitter experience suggests that it is impossible to anticipate every requirement. For this reason, structured cabling is preferred over dedicated runs.
Structured cabling is simply the installation of a standard cable type throughout the building ("flood wiring"), which is terminated using an industry standard connector and can then be used for multiple purposes. The most common choice is category 5 cable (usually abbreviated to cat5), or the slightly superior cat5e. Cat5 cable is primarily intended to be used for computer networking, but can also carry a variety of other low voltage signals safely and reliably - including certain formats of video signal, telephone, whether analogue and digital, alarm signalling and line-level audio signals. Cat5 is not suitable for power distribution or high current applications, such as driving hi-fi loudspeakers, and it cannot be used to distributed UHF or VHF signals (such as those used for terrestrial TV). Cat5e is physically very similar to Cat5, but offers the potential to support faster networking equipment than cat5. The cost differential is such that it makes little sense to deliberately install cat5 cable instead of cat5e cable. End fittings such as faceplates and patch panels also need to be cat5e rated, and these can be significantly more expensive than their cat5 counterparts, but can be readily upgraded later if required.
Location of Node Zero
In selecting node zero, try to choose a location which is:
- Is convenient for cable runs. Laying cables is always inconvenient - but some locations, such as stair wells are better suited than others.
- Has easy access. Even if you don't plan to install much equipment at the outset, it will inevitably accumulate, and some of it, such as racks and uninterruptible power supplies, is both big and heavy.
- Is well ventilated. The more stable the operating environment in terms of temperature, the more reliable equipment will be. Hard disks are particularly temperature sensitive, and will fail if you shut the PC in an unventilated cupboard. For similar reasons, the attic is also generally a poor choice.
- Has ample electrical outlets. For obvious reasons.
- Has access to basic services - including incoming telephone lines, and TV feeds - whether terrestrial, cable TV feeds (including broadband connections), or satellite.
- Is secure. A location which is out-of-sight is less likely to attract to attention. Outbuildings and garages are generally a poor choice from a security perspective.
In some houses it may be more convenient to have split Node Zero between two different locations - perhaps with one upstairs and the other downstairs, with interconnections between the two.
Equipment Racks
As equipment and cables accumulate, they become increasingly difficult to manage. One of the most effective solutions is to use professional 19" racks to house the equipment. Such racks are typically used in IT machine rooms, and although they are expensive new, they can be purchased second hand at reasonable cost. In searching for a rack, try to source one with all the fittings that are required - accessories such as shelves, doors and wheels are also surprisingly costly. Both E-Bay and Display Electronics are good sources of the racks themselves.
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