However, installing cables in special enclosures has far-reaching ramifications: unexposed cabling complicates maintenance and makes visual inspection difficult, which can hide progressive damage until it results in complete communication failure. This, along with the fact that no means of external protection can replicate indoor conditions, makes cable selection the determining factor in designing CCTV cabling installation.
High-quality insulating materials can be augmented, but never replaced, by enclosures and conduits. External-grade cables are designed to withstand a higher level of environmental stress than internal-grade cables; they use special materials for the insulation and shielding layers, and consequently last longer and are less likely to fail unexpectedly.
The quality of the cable’s insulator is not the only concern which influences cable selection. In fact, the primary factors involved in this decision are bandwidth and power requirements.
Cables installed outdoors are not only exposed to weather and dust, they are exposed to a higher level of radiation and interference than indoor cables. Therefore, cabling installation guidelines and standards impose slightly higher requirements related to noise immunity – all in order to guarantee the bandwidth required by modern electronic security systems.
Industry-specific guidelines such as the Building Industry Consulting Service International’s (BICSI) Electronic Security Systems Design Reference Manual (ESSDRM), or the ANSI/BICSI 005-2016 standards go into great detail about which cable types to use for each component of a security system. The requirements are, in fact, far too detailed to discuss at length here, but a few often-overlooked guidelines can be distilled.
Modern Ethernet cables are twisted-pair copper cables: the way electromagnetic fields behave makes it very useful to twist wires as tightly together as possible, minimising the surface between each pair of wires – hence the name “twisted-pair”. Simply braiding the eight copper wires of an Ethernet cable is usually enough to maintain good signal integrity for unpretentious indoor deployment, but is almost always insufficient for CCTV cabling.
One way to offer additional immunity to EM interference is to “dress” these twisted pairs of cables in one or more additional metal foils, called shields (when they cover each pair individually), foils or braid screens (when they cover all pairs together). Such cables (STP, SFTP, S/UTP and F/UTP) offer far better immunity than unshielded (UTP) cables and are often the only ones which are appropriate for security cabling, especially in high-interference environments, such as manufacturing floors or London offices that make extensive use of wireless equipment.
Installing shielded cables is not entirely trivial, though: in order for the shielding to be effective, it needs to be electrically grounded, which requires specific procedures and materials in order to be done properly, and high-quality measurement equipment in order to confirm proper installation.
Furthermore, EM interference is usually not just mitigated by using cable shielding, but also minimised by adequate cabling design. CCTV cabling installation guidelines and standards recommend or require that signal cables not run close to mains power cables or other low- or high-voltage cables, for example – an implementation solution that can dramatically reduce troubleshooting expenses, but which requires significant planning effort.
The last concern that we mentioned is the proximity to potentially malicious actors. This is, perhaps, the most unique trait of security cabling. Immunity to environmental factors and electrical interference is required in other types of networking. However, security cabling must withstand not only the accidental influence of environmental factors but also the deliberate action of potential intruders.
When it comes to protection against tampering, proper installation is the main defence mechanism. NCP109 recommends that cables be installed only within areas that can only be accessed by the presentation of a valid credential (known as controlled areas) and using suitable protection when that is not possible. CCTV cabling is inherently one of the sections of a network’s cabling which cannot run only through controlled areas, which is why it typically requires at least some basic form of protection in some areas. Standard cable conduits, trunking and armour are deployed as means of protection, and while the planning effort they involve is non-trivial, most of the effort is involved in proper installation, as it requires special tools and skills.
