The November Integrated Building Systems column covered the basic business and planning requirements for systems integration. Now, let’s kick it up a notch and review connectivity infrastructure.
(Note: part 1 is here.)
Systems integration makes parts of a system—e.g., lights and controllers, blowers and thermostats, cameras and monitors—work together. It’s also a way of making different systems—e.g., heating, ventilating and air conditioning (HVAC); lighting; security; and fire alarms—work together.
Integration requires the exchange of information between each of these systems or system pieces. There have to be connections between them (connectivity). The last column mentioned there are three ways of making these connections: copper wire, optical fiber and wireless transmission.
I consulted many sources for the best connection solutions. Steven Kenney, communications expert and marketing manager for Hitachi Cable Manchester (HCM) said the type of connection chosen depends first on the requirements of the electronics in the equipment being integrated.
It also depends on whether large volumes of data need to be transferred or if the system can work as well at lower rates. Some end-users may be fine with an infrastructure that will support 100 megabit, as contrasted, for example, with financial institutions, which may regularly update their electronics to have the latest and greatest. If you have an Internet protocol (IP) camera and want to send detailed video information to a monitor in a central security office, you need cabling that can accommodate that data without distortion or a weakening signal strength (attenuation).
Transmission volume and speeds are growing at a rate that no one had anticipated. For a financial institution or a hospital, throughput (the rate at which data is moved) needs are likely to increase; it would be wise for those types of facilities to install Category 6a cabling, which will support 10 gigabit Ethernet and everything that preceded it. That way, you know all the required accessories, such as plugs and jacks, also will support 10 gigabit Ethernet if they’re rated Cat 6a.
A warranty covering performance is important to many users. A solid warranty means quite a bit for end-users who plan on using their cabling infrastructure for a long time, e.g., a police station or high school. A warranty also indicates the manufacturer’s confidence in their product quality.
ANSI/TIA/EIA-568-A, a performance specification for unshielded twisted-pair (UTP) and shielded cables was ratified in 1991 and has since been periodically updated. The current standard is 568-C. That’s the source of the well-known category ratings for UTP cable. Currently, we have Category 3, which will meet stated performance requirements up to a frequency of 16 MHz; Cat 5e to 100 MHz; Cat 6 to 250 MHz; and Cat 6a to 500 MHz. Using standard ratings comes with the benefit of being able to compare one cable to another without having to rely solely on the manufacturer’s claims.
Frequency versus throughput
Gigabits per second is a measure of throughput, which is related to frequency—higher frequency rated cable can handle higher throughput—but the relation stops there. Throughput in bits (mega- or giga-) is a measure of the rate at which data can be carried. A bit is one data point, which is encoded on a carrier frequency. The number of bits that can be transferred per second has to do with the scheme with which the data is encoded. An online article titled “Megahertz, Megabits, MegaConfusion” (www.siemon.com) has a good discussion of this.
How to decide
Good infrastructure design to ensure a workable building systems integration depends on a number of factors, both technical and nontechnical. The higher the data transfer rate, the more expensive the cabling and equipment. That expense has to be justified. If the installation is in a small company with just a few automated building systems, it might not be as important to offer the highest speeds available. On the other hand, the trend in equipment for systems is to migrate toward high-speed data transfer. Consider hospitals, which are using Ethernet LANs to transfer X-rays and IP video; those facilities’ needs are steadily increasing and can be expected to continue to grow.
The cost of pulling out old cable to replace it with cable that will operate at faster rates is very expensive. Cabling infrastructure should be viewed as an asset, enhancing a building’s value. The value of that asset is increased if you know that the cabling infrastructure will not just function well with existing systems but can be expected to be compatible with new developments for years to come.
BROWN is an electrical engineer, technical writer and editor. For many years, he designed high-power electronics systems for industry, research laboratories and government. Reach him at firstname.lastname@example.org or at www.writingengineer.com, an independent professional writing service.