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Introduction to Network Communications

Electrical article index page

Ross Ignall , Dranetz-BMI



The Power Platform PP1-R is the first power quality analyzer to offer Ethernet network communications. Up until now, telephone line modems and RS232 were the only standard way for remote communications. These devices work well but are slow in comparison to computer networks. Today's fastest consumer modems offer only 33 thousand bits per second transfer rates. Ethernet network communications transfer data at 10 million bits per second. This is about three hundred times faster than the fastest modems.

The plug and play communications feature of the PP1-R allows the user to make the choice of either Ethernet network or modem. It literally takes seconds to change from one type to the other. In fact, in a semi portable application, the user can swap back and forth between Ethernet and modem in seconds depending upon which is available.

As you can see from the large speed improvement, network communications should be used if available. Since network communications are new to some people, this guide is meant to help introduce Ethernet networking and how it applies to the PP1-R.


What is a Network?

A network is a data communications system that links two or more computers together. The wide scale use of networks in recent years has revolutionized the way computers are used both in business and in the home. In the office, most computers are now tied together via networks to share data or devices such as printers and send electronic mail (e-mail). The advent of the Internet has now brought networking into the home to allow individuals to send e-mail and share information with the rest of the world.

The actual media or physical connections used to link these computers over a network vary greatly. Copper wire and fiber optic cable are two popular types in use today. Most offices use copper wire within the building to connect individual computer together and use fiber or other connections to link buildings together across great distances.

What is Ethernet?

The Ethernet network as it's known today is a standard developed by The Institute of Electrical and Electronics Engineers (IEEE). IEEE standard 802.3 defines how to connect computers together in an Ethernet network. It's the low level definition of the actual cable used and how information is passed through the cable.

Each computer or other device connected to the Ethernet network must contain hardware and software that conforms to this specification. An important thing to remember is that unless you are a network administrator or otherwise involved in networking you don't have to be concerned with how this works. Standard off the shelf hardware and software is used in each computer to handle this and seamlessly integrate Ethernet into your computer.


Types of Ethernets

As mentioned above, IEEE standard 802.3 defines the cabling used in an Ethernet network. The most popular types in used today are thinnet (10Base2) and unshielded twisted pair (10BaseT).

The names 10base2 (coax) and 10baseT (UTP) describe the cable used and other details of the network. The number 10 refers to the speed of the network in millions of bits per second. Therefore, both coax and UTP operate at 10 million bits per second.
Below is further description of each type.

Thinnet (10base2)
Thinnet Ethernet, which is also referred to as 10base2, uses a coaxial cable similar to what used in cable television. Thinnet Ethernet is arranged in what is called a bus type network. Simply stated, this means there is a long wire with many devices connected to it.

Each device connects to the network via what is called a `T' connector. As shown in figure XXXX, as its name implies, the T connector looks like the letter T. Its purpose is to allows each device to connect to the network without breaking the wire. A good analogy is a water pipe with several fixtures attached to it. T fittings are used to carry water to each fixture connected to the pipe. The T connector brings the Ethernet to each device.

Another point to know about thinnet is that each end of the wire has to have a terminator connected to it. The purpose is to electrically terminate the wire to optimize its performance. To continue the plumbing analogy, a water pipe needs a cap or other fitting on each end to prevent leaking. A terminator is a small fitting that screws into the open end of the T connector.

Why use thinnet? There are two main advantages of thinnet over UTP. 1) Due to the shield in the coaxial cable, Thinnet is more immune to electrical noise than UTP, 2) Longer wire lengths can be used in thiinet. The maximum wire length for thinnet is about 600ft while UTP is 300ft.

UTP (10BaseT)
The UTP (Unshielded Twisted Pair) Ethernet, which is also referred to as 10baseT, uses cable that is very similar to telephone cable. UTP Ethernet is arranged in what is called a star type network. Like a telephone system, each device is connected to a central distribution point via a single wire. Therefore, each computer (or PP1-R) has a single wire connected to it.

Why use UTP? UTP is less prone to failure due to wiring problems or device problems. Since each device has its own wire, if the wire were to break, the other devices will remain unaffected. In thinnet, if the wire were to break, all devices would be affected.

The flexible communications of the PP1-R supports both UTP (10baseT) or thinnet (10base2) Ethernet networks. If for some reason your facility does not have either of these types available, adapters are commercially available to convert from other types to the coax and UTP supported by the PP1-R.

The PCMCIA Ethernet card within the instrument can support either type of connection but cannot support both simultaneously. Therefore, the customer must order the proper Ethernet option when purchasing a PP1-R. The instrument remains the same but a different Ethernet cable, or media adapter, is used within the instrument to connect the PCMCIA Ethernet card within the instrument to the rear panel. If you need to switch between UTP and coax when moving the instrument throughout a building you can order the PP1-R with both types and easily convert from one to the other as the need arises.


What is a Protocol?

The Ethernet standard described above defines the wiring of the network and how the computers tied to the network are to share the same cable. Ethernet defines how the wire is used, not how computers are to communicate with each other. This is where network protocols come in. Network protocols define how computers should identify each other on the network and how data is transferred between computers. Some common protocols in use today are IPX/SPX and TCP/IP. The PP1-R uses the industry standard IPX/SPX protocol which is one of many protocols built into Windows 3.11, Windows 95, and Windows NT.

The Ethernet standard is protocol independent. This means that many protocols can share the same Ethernet network without interfering with each other. Therefore, PP1-R's can be used on most Ethernet networks even if the network does not use the IPX/SPX protocol used by the PP1-R. As an example, if your facility uses TCP/IP, the IPX/SPX protocol used by the PP1-R can coexist on the network without a problem.

Although Ethernet is protocol independent, it is important to note there may be cases where the network hardware does not support a particular protocol. Some networks have dedicated network control devices such as routers that help manage the traffic on the network. These devices have the ability to pass or reject certain protocols. In most cases, these devices support the protocol needed but have to be configured to do so.

Before installing the PP1-R system, ask your MIS or computer department if your network supports the PP1-R protocol. Specifically tell them the PP1-R uses the IPX/SPX protocol with NETBIOS transport

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