Demystifying Wired Communications for IP-Based Security Applications

STP
Typically, STP cable is only used (for high-speed data) when there is no other option available or where such cable is already in place and cannot be replaced (such as a telephone line). There are devices available to run Ethernet over STP [search “Ethernet over single twisted pair”]. Quite long distances can be achieved with DSL technology developed for broadband connections, but typically the data rates fall off quite sharply with increasing distance.

EoC
There are vast lengths of coaxial cabling installed all over the world, originally installed for analog CCTV cameras. Indeed, despite the dramatic surge in network camera sales, the vast majority of surveillance cameras are still analog, and most of them are connected with 75-ohm coaxial cable of varying types and quality. As these cameras are replaced with network ones, this legacy coaxial cable can be reused as a full-speed, 100-Mbps Ethernet link by using powered Ethernet-over-coax (EoC) adaptors.

There are a number of EoC solutions available on the market [search “Ethernet over coax“]. Many are designed for domestic applications (using TV cabling infrastructure), and these are generally unsuited to professional security applications (the units are too big, have wrong connector types, exhibit lower robustness, have specific/custom power supply requirements, and offer poor support and limited performance and diagnostics). However, a number of companies have focused on solutions for the surveillance market in particular, and many consultants, specifiers and integrators are taking full advantage of these.

Reusing installed coaxial cabling has a number of significant advantages: no new cabling needs to be pulled; installation time is reduced; business disruption for the customer is minimised; environmentally, it is good to “recycle” the existing cabling; even long cable runs of 200 meters or even 300 meters will still run at 100 Mbps without repeaters. Further, by using multiport EoC adaptors at the camera end, multiple network cameras can be streamed over a single coaxial cable, thus providing a very cost-effective way of increasing camera count with minimal extra cabling. Note also that these EoC connections can be used for any networking connection, such as IP access control, VoIP, IP alarm systems, building management or multiples of those, with or without concurrent IP video.

[Side note: In discussing coax as a medium which can be reused for digital video transmission, we should not ignore the technological approach of the HDcctv Alliance. However, to compare the very product-specific technology of HDcctv with the much more general solution of EoC requires more space than is available here and will be the subject of a future article].

NO SILVER BULLET
PLC is not a great solution for professional security applications and is more suited to domestic applications including home automation. Ethernet over PLC suffers from signal interference and can have unpredictable performance. Twisted-pair cabling is normally only relevant when better options are not possible for whatever reason.

Ethernet is an almost universal solution on CAT5e/6 cabling, with security-specific distance problems overcome by PoE-powered LAN extenders. Existing coaxial cables which were originally installed for analog video can also reused for fast Ethernet segments and removes a significant market restraint on the conversion from analog to IP-based video.



Product Adopted:
Fiber-Optic Transmission
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