The Interconnected Home - Part 1

A (Very) Brief History of Communications to the Home

We are experiencing a revolution in communication and control systems that is changing the way we live.

For a long time there were two major systems of distributed electrical wiring coming into homes: power and telephone, and oh yes, one minor system — cable TV. The revolution developed slowly at first, and on two different fronts. There was the development of communication and control technology and the changes in the Federal regulations governing these systems.

Power and telephone companies were granted monopolies by the government in order to maintain uniformity in the delivery of these services. This system of monopolies began to weaken in 1984 when a Federal judge issued a decree ordering the breakup of the telephone monopoly held by AT&T and its local Bell telephone subsidiaries. The next big step came when congress passed the Telecommunications Act of 1996.  This law removed many of the rules that prohibited players from one part of the telecommunications industry, like telephone, from providing services in other sectors, like cable TV. Once all of these companies were free to compete, the technology, which had been quietly developing, started mushrooming. Telecommunications became a means of transmitting video and data in addition to voice.

Another key development was the spread of personal computers (PCs) in the business world. The key to having a computer on every desk was developing a standard way they could talk to each other—to send information back and forth. In the 1980s at about the time PCs first hit the market, work was begun on developing a communication standard for computers. There were several competing systems but the one that won out and is pretty universally accepted today, is Ethernet. The first Ethernet connections between computers were run on coaxial cable. As the numbers of computers linked on a single network (Local Area Network) grew, coax became cumbersome and expensive. At the same time many buildings had plenty of excess installed unshielded twisted pair telephone cable. This was the beginning of what we now know as the 10BASE-T UTP Ethernet standard. This was the start of the category rating system, the first being Category 3.

Another important development that was going on at the same time was the birth of programmable logic controllers (PLCs) for controlling and getting information about manufacturing processes. They were developed in response to a specification issued by General Motors in 1968. These days most factories that manufacture large numbers of products use automatic systems based on PLCs. By the way you can see a little bit of history in that PLCs were originally called PCs (programmable controllers), but the personal computer revolution far outstripped them so they had to change their name.

Convergence

The next key step, and one that is still continuing, is convergence. It probably started on the factory floor. There were often separate PLCs controlling each process station, so to really automate the system, PLCs had to communicate with each other. They also had to communicate with programmable devices such as temperature and motor speed controllers. At first, most manufacturers used proprietary systems, but that was a limiting factor. In order to be able to use devices made by different manufacturers, it made sense to develop open systems of communication based on a shared publicly available standard. Since Ethernet was already available it was often chosen. Using Ethernet also meant that the operations on the shop floor could send data to management in real time.

The Coming Residential Revolution

The kinds of integration that have become commonplace in commercial settings, factories, educational and health care facilities, have so far not made a big impact on residential systems—but they will. The only question is when. What will drive home networking is the coming of Smart Television. Already starting to appear on the market, smart TVs allow direct connection to a home computer network so that anything available on your PC can be accessed via your TV set. Online content such as movies, video, music as well as standard TV shows will be able to be delivered directly “on demand” and in high definition. Once TV is tied into home networks, it would make sense in order to save energy and improve life safety, to tie temperature control, lighting, fire alarms, intrusion detection and access control to the same network. And all of these systems could be monitored and controlled by any computer in your home, as long as it is connected to the network.

The Wired Home

This will rely on a wired system that can reliably carry all of the data required for this networking and carry it at speeds high enough so that all of the connected devices operate smoothly. The key to moving these signals about the home is Category rated unshielded twisted pair (UTP) cabling. The Category rating system is a means of guaranteeing that wiring and connection devices that adhere to it will meet guaranteed minimum standards for transmitting data.

Data Transmission Terminology—a Brief Technical Review

The terminology surrounding network cabling and devices can get a bit confusing. Some of the most talked about terms are data rates (in gigabits per second), frequency and bandwidth (in megahertz).

• Frequency is one of the basic parameters used to describe cable. Frequency is simply the number of times per second the voltage and current signals reverse themselves from positive to negative and back again. If the frequency becomes too high for the pair of wires that’s carrying the signal, the cable will act like a short circuit and nothing will get through. The frequency rating of a cable is the maximum rate at which it can carry a signal without distorting it. Bandwidth is this maximum rated frequency.
• Digital signals are made up of 1s and 0s arranged in a pattern, which encodes the information being transmitted. These 1s and 0s are called bits. Designers are constantly looking for ways of sending more bits per second by coming up with clever coding schemes that don’t raise the frequency.
• The electrical signals can be transmitted on a cable at a frequency that is no higher than the rated bandwidth. But within these limits, there can be significant differences in the rate at which information can be transmitted since information is encoded in bits. The number of bits per second can vary according to the scheme that is used to encode them. Bit information can be sent using different techniques such as modulating amplitude, frequency or phase.

To sum it up, frequency (or bandwidth) rating is given in Hertz (cycles per second), for example 100 MHz (megahertz) is a hundred million cycles per second. This is a uniform way to rate a cable and can be used to compare one cable with another.

Bit rate is given in bps (bits per second), for example, 100 Mbps (megabits) is a 100 million bits per second. The bit rate is dependent on the particular system you’re using to encode the bit information onto the carrier signal.

Standards

The development of standards for LANs (Local Area Networks) and for the cables used to build them has made it possible for the explosive growth of computer-based communication and control. Ethernet was developed in the 1980s and has remained the major standard for transmitting data. The Ethernet standard was published by a committee of the IEEE as 802.3. It is based on a series of rules that allow all interconnected devices to talk with each other. Its beauty, and the reason for its long survival, is that it can continue to be used, even as equipment gets much more sophisticated and transmission speeds go up by factors of 10 times.

IEEE 802.3 is based on the OSI (Open Systems Interconnection) model, which reduces every design and communication problem into a number of layers. For Ethernet, it specifies two different layers, the physical layer and the data link layer. The physical layer specifies the type of cable—four unshielded twisted pairs, the type of connector (RJ45) and pin layout, voltages used for the bits and some other physical details. The data link layer specifies a system for conveying information with digital bits (1s and 0s). Each device on the network has a unique identifying address—a MAC (Media Access Control) address. The data link protocol specifies that messages are made up of individual digital bit packets, called frames. The frame is a sequence of bits in a specified order, signaling the start, destination, source and actual message content plus a few other signals. Therefore a whole series of bits has to be transmitted in order to send one piece of useable information.

The Category System

In the 1990s, the Telecommunications Industry Association (TIA), an offshoot of the Electronic Industries Alliance (EIA), developed a set of standards for Ethernet cables—TIA/EIA-568. One of the many important outcomes of this work was the decision to use a standard cable arrangement, which would consist of four twisted pairs, each pair being twisted separately. This was the start of the Category standards for UTP high-speed cable. They also described a standard connector for these eight wires — RJ45.

The purpose of twisting is that the magnetic fields around each wire of the pair cancel each other so that electrical interference from and to outside sources is minimized. Each pair also has a different twist length to limit crosstalk between the pairs.

UTP is an inexpensive, easy to install method of providing high-speed data connections between digital devices. The development of UTP parallels the development of the Ethernet as the primary means for running LANs. The initial Category rated UTP cable was CAT 3, which was designed to transmit Ethernet data at 10 Mps (megabits per second). Its specified bandwidth is 20 MHz. This Ethernet protocol was called 10BASE-T. The 10BASE-T Ethernet standard was approved by the IEEE in 1990 and the CAT-3 standard for wiring 10BASE-T LANs was approved by the TR-42 committee in 1991.

Category 3 cable uses two of the four cable pairs and is no longer used in new installations because Category 5 was approved in 1995 to transmit data at 10 times the rate of what CAT 3 could handle. 100 Mps (100BASE-T) Ethernet was approved in the same year.

The general trend has been towards developing faster and faster Ethernet systems and cables to match.

The Importance of Standards

It is important to understand that if two UTP cables from two different manufacturers both meet the CAT 5e standard, this does not mean that the two cables will have identical performance. It is possible that one may be able to run a particular application but the other may not. However the Category rating means that if, say you want to run 1000BASE-T Ethernet, you are guaranteed that CAT 6 cable will do the job—assuming all of the other components in your system, such as plugs and jacks are also rated for Category 6 and that the installation is done properly. This means that the wires are untwisted at the connector by no more than the specified length. Also, for example, care has to be taken that the pin assignments at each end of the cable match properly. For example the TIA/EIA spec for UTP specifies T568A and T568B connections for different functions. But it’s possible that some cables rated CAT 5e might also work. It’s important to understand that the cabling standards assure a minimum level of performance. There are many performance specs on cables so it is wise when selecting one for a particular application, to check with the application provider to be sure that your cabling system is adequate.

Summarizing

To summarize—the importance of these standards is that you can be sure that when you buy a cable with a Category label it will meet the requirements of the Ethernet standard as specified in the table. Not only that, but each cable is backwards compatible so that CAT-6A, for example, can be used for any application that runs on Categories 6, 5e, 5 or 3. Running Category rated cable throughout a home will enable all of the digital devices in a home to easily interact with each other and be coordinated by any connected computer. As far as best performance now and in the future, it would make sense when rewiring an older home or building a new one, to use Category 6A cable since it will be compatible with the high-speed systems that are coming down the road and will still be capable of running older, slower devices. Some experts think that CAT 6 will good enough for home systems in the near future and that people might find it hard to justify the price difference between 6A and 6. However it might be less expensive in the long run to install 6A now rather than discovering 5 to 10 years from now that CAT 6 won’t support the latest high tech equipment.

Useful Resources

Have questions regarding Structured Wiring, a component being incorporated into more and more homes? For an overview, order a FREE copy of Structured Wiring For Today's Homes CD-ROM - Homeowner Edition.

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Phone wiring isn’t just for phones anymore. Ordinary telephone wiring can’t handle today’s rapidly expanding communications needs. Today’s homeowners expect their homes to accommodate:

• Multiple phone lines
• Internet service
• Video distribution, and other entertainment services
• Data and security services
• Fax machines
• And the list goes on.

Faster and more reliable than ordinary phone wiring, low-cost, high-tech copper wiring (Category 5 or better) should be installed to every room in the modern home. It’s what is needed to carry voice, data and other services from where they enter the house to every room, and from any one room to any other.

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