Even though the Internet is still a young technology, it's hard to imagine life without it now. Every year, engineers create more devices to integrate with the Internet. This network of networks crisscrosses the globe and even extends into space. But what makes it work?
To understand the Internet, it helps to look at it as a system with two main components. The first of those components is hardware. That includes everything from the cables that carry terabits of information every second to the computer sitting in front of you.
The reasons our program works, the how and why of recovery, are found in the collective wisdom of our members, presented here in twenty-four essays on NA’s Steps and Traditions. To the member: This book is a discussion of the Twelve Steps and Traditions of NA, meant to help you determin. An NA group is a powerful example of a Power greater than ourselves at work. Often in desperation, we enter a room full of addicts who share their experience, strength, and hope with us. As we listen, we know with certainty that they have felt the hopelessness and remorse from which we, too, have suffered. How It Works If you want what we have to offer, and are willing to make the effort to get it, then you are ready to take certain steps. These are the principles that made our recovery possible: 1. We admitted that we were powerless over our addiction, that our lives had become unmanageable. We came to believe that a Power greater than ourselves. The Upper Cumberland Area Outreach/Website Committee would like to thank the members that have contributed documents to our site. Those contributions have helped fill in holes back in the 70’s and 80’s and provided insight into how the WSC Quarterly meetings were held to support the work of the WSC Sub-Committees.
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Other types of hardware that support the Internet include routers, servers, cell phone towers, satellites, radios, smartphones and other devices. All these devices together create the network of networks. The Internet is a malleable system -- it changes in little ways as elements join and leave networks around the world. Some of those elements may stay fairly static and make up the backbone of the Internet. Others are more peripheral.
These elements are connections. Some are end points -- the computer, smartphone or other device you're using to read this may count as one. We call those end points clients. Machines that store the information we seek on the Internet are servers. Other elements are nodes which serve as a connecting point along a route of traffic. And then there are the transmission lines which can be physical, as in the case of cables and fiber optics, or they can be wireless signals from satellites, cell phone or 4G towers, or radios.
All of this hardware wouldn't create a network without the second component of the Internet: the protocols. Protocols are sets of rules that machines follow to complete tasks. Without a common set of protocols that all machines connected to the Internet must follow, communication between devices couldn't happen. The various machines would be unable to understand one another or even send information in a meaningful way. The protocols provide both the method and a common language for machines to use to transmit data.
We'll take a closer look at protocols and how information travels across the Internet on the next page.
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You've probably heard of several protocols on the Internet. For example, hypertext transfer protocol is what we use to view Web sites through a browser -- that's what the http at the front of any Web address stands for. If you've ever used an FTP server, you relied on the file transfer protocol. Protocols like these and dozens more create the framework within which all devices must operate to be part of the Internet.
Two of the most important protocols are the transmission control protocol (TCP) and the Internet protocol (IP). We often group the two together -- in most discussions about Internet protocols you'll see them listed as TCP/IP.
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What do these protocols do? At their most basic level, these protocols establish the rules for how information passes through the Internet. Without these rules, you would need direct connections to other computers to access the information they hold. You'd also need both your computer and the target computer to understand a common language.
You've probably heard of IP addresses. These addresses follow the Internet protocol. Each device connected to the Internet has an IP address. This is how one machine can find another through the massive network.
The version of IP most of us use today is IPv4, which is based on a 32-bit address system. There's one big problem with this system: We're running out of addresses. That's why the Internet Engineering Task Force (IETF) decided back in 1991 that it was necessary to develop a new version of IP to create enough addresses to meet demand. The result was IPv6, a 128-bit address system. That's enough addresses to accommodate the rising demand for Internet access for the foreseeable future [source: Opus One].
When you want to send a message or retrieve information from another computer, the TCP/IP protocols are what make the transmission possible. Your request goes out over the network, hitting domain name servers (DNS) along the way to find the target server. The DNS points the request in the right direction. Once the target server receives the request, it can send a response back to your computer. The data might travel a completely different path to get back to you. This flexible approach to data transfer is part of what makes the Internet such a powerful tool.
Let's take a closer look at how information travels across the Internet.
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In order to retrieve this article, your computer had to connect with the Web server containing the article's file. We'll use that as an example of how data travels across the Internet.
First, you open your Web browser and connect to our Web site. When you do this, your computer sends an electronic request over your Internet connection to your Internet service provider (ISP). The ISP routes the request to a server further up the chain on the Internet. Eventually, the request will hit a domain name server (DNS).
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This server will look for a match for the domain name you've typed in (such as www.howstuffworks.com). If it finds a match, it will direct your request to the proper server's IP address. If it doesn't find a match, it will send the request further up the chain to a server that has more information.
The request will eventually come to our Web server. Our server will respond by sending the requested file in a series of packets. Packets are parts of a file that range between 1,000 and 1,500 bytes. Packets have headers and footers that tell computers what's in the packet and how the information fits with other packets to create an entire file. Each packet travels back up the network and down to your computer. Packets don't necessarily all take the same path -- they'll generally travel the path of least resistance.
That's an important feature. Because packets can travel multiple paths to get to their destination, it's possible for information to route around congested areas on the Internet. In fact, as long as some connections remain, entire sections of the Internet could go down and information could still travel from one section to another -- though it might take longer than normal.
When the packets get to you, your device arranges them according to the rules of the protocols. It's kind of like putting together a jigsaw puzzle. The end result is that you see this article.
This holds true for other kinds of files as well. When you send an e-mail, it gets broken into packets before zooming across the Internet. Phone calls over the Internet also convert conversations into packets using the voice over Internet protocol (VoIP). We can thank network pioneers like Vinton Cerf and Robert Kahn for these protocols -- their early work helped build a system that's both scalable and robust.
That's how the Internet works in a nutshell. As you look closer at the various devices and protocols, you'll notice that the picture is far more complex than the overview we've given. It's a fascinating subject -- learn more by following the links on the next page.
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More Great Links
Sources
- Computer History Museum 'Computer Pioneer Robert Kahn with Ed Feigenbaum.' YouTube. Jan. 9, 2007. (April 23, 2010)http://www.youtube.com/watch?v=t3uTKs9XZyk
- Congressional Digest. 'Internet History: From ARPANET to Broadband.' February 2007. pp. 35 - 37, 64.
- Hauben, Ronda. 'From the ARPANET to the Internet.' Columbia University. June 23, 1998. (April 26, 2010) http://www.columbia.edu/~rh120/other/tcpdigest_paper.txt
- Information Sciences Institute. 'Internet Protocol.' September 1981. (April 26, 2010) http://www.ietf.org/rfc/rfc791.txt
- Opus One. 'What is IPv6?' (April 27, 2010) http://www.opus1.com/ipv6/whatisipv6.html
- THINK project. 'A Technical History of the ARPANET.' The University of Texas at Austin. (April 26, 2010) http://userweb.cs.utexas.edu/users/chris/nph/ARPANET/ScottR/arpanet/index.htm
Sodium Lamp
High lumen output at high efficiency(1920 - Today)
| Introduction |
| HPS Lamps |
| Inventors of the HPS |
Sodium Lamps were first produced commercially by Philips in Holland in 1932. There are two kinds of sodium lights: Low Pressure (LPS) and High Pressure (HPS). These lamps are mostly used for street lighting as well as industrial uses.
The lamp works by creating an electric arc through vaporized sodium metal. Other materials and gases are used to help start the lamp or control its color. See the photos lower on this page for more details.
All credits and sources are located at the bottom of each lighting page
THE LOW-PRESSURE SODIUM LAMP
The LPS lamp was the first sodium lamp to be developed. It is known by its signature monochromatic yellow color. It is mostly used in Europe since it did not appeal in other markets due to its poor CRI or color rendering. It is among the most efficient lamps in the world because it uses all the current it gets to create light at the most sensitive color (frequency) to the human eye. An incandescent lamp in contrast creates light at all frequencies from Infrared (non-visible) to UV at the other end of the spectrum. The energy used to make non-visible light is a waste of energy since it does not help do the principle job of an electric light. The LPS lamp is also called a SOX lamp (SO for sodium)
Advantages:
- Very efficient lamp
- Powerful lamp for use of large areas
- Despite a warm up time of 5-10 minutes it restarts immediately if there is a brownout
- Lumen output does not drop with age (such as in LEDs or incandescents)
Disadvantages:
- Worst color rendering of any lamp
- Sodium is a hazardous material which can combust when exposed to air (such as if the bulb is broken in the trash)
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Common Uses: Outdoor lighting, security lighting, long tunnel lighting (the light seems to give less fatigue in tunnel driving than white lights flashing by at close proximity).
1. How a modern LPS lamp works
2. Inventors and Developments
1. How the LPS lamp Works
The LPS Lamp is mostly in Europe for outdoor lighting. They create a monochromatic yellow light. In the diagrams below you will see how as it starts it creates a red glow due to the neon gas. The neon gas lights at a lower temperature. As the temperature increases the sodium begins to vaporize and the lamp turns to a pure yellow.
An LPS with it's yellow glow
Argon has a lower glow voltage, argon helps the smaller lamps start at a lower voltage. The larger LPS lamps used in street lighting for the most part do not use argon.
2. LPS Development and Inventors:
Low pressure sodium lamps were invented first in 1920 by Arthur H. Compton at Westinghouse. The first lamp was a round bulb with two electrodes on each side. The solid sodium metal remained on the bottom center of the bulb. When heated up the metal would vaporize and the lamp would glow yellow. The lamp had to be designed in a sphere because after the metal cooled when the lamp was turned off, the sodium has a property of migrating to the coolest part of the bulb where it solidifies. A tube design would be more particle, similar to the neon lamp which had already been developed by 1920, but it was found that the sodium would migrate to the outer ends of the tube, and there the sodium would destroy the electrodes over time as well as not get hot enough to vaporize. The problem with Compton's models is that the highly corrosive sodium would attack and blacken regular silica glass.
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1932 - The first sodium lamps for commercial sale were made by Philips. Philips has not released the names of the individuals who did the monumental work of developing a reliable sodium lamp ready for widespread use. The first lamps had a removable outer jacket with a vacuum between glass to insulate the bulb to keep it hot enough to keep the sodium in vapor form.
Later developments include:
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-Integrating the outer vacuum jacket as a bulb with the inner discharge tube inside, therefore eliminating the separate outer jacket and improving insulation properties.
-Indium tin coating on the inside of the outer jacket to reflect infrared (heat) waves back to the bulb, keeping it warmer and improving reliability in cold weather.
High Pressure Sodium Lamp (HPS Lamp)
The HPS lamp is the most ubiquitous lamp for street lighting on the planet. The lamp is an improvement over the LPS lamp in that it has more acceptable color with the great efficiency of the sodium lamp. The better color rendering comes with a bit of sacrifice, it has less efficiency than the LPS. General Electric first developed the lamp in Schenectady, New York and Nela Park, Ohio. The first lamp came on the market in 1964.
An HPS lamp with a starting strip, it uses a xenon starting gas. |
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1. HPS: How it Works
The HPS lamp consists of a narrow arc tube supported by a frame in a bulb. The arc tube has a high pressure inside for higher efficiency. Sodium, mercury and xenon are usually used inside the arc tube. The arc tube is made of aluminum oxide ceramic which is resistant to the corrosive effects of alkalis like sodium.
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Maintaining a vacuum is difficult, oxygen and other gasses can seep in over time. The getter keeps a stable vacuum by sucking out remaining oxygen and unwanted gasses. The sodium is stored often stored in the amalgam reservoirs on the ends of the arc tube when it is cool unlike the LPS lamp where the sodium is stored in the bumps on the side of the tube (see LPS diagrams)
Disposal:
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The Sodium in these lamps is a highly volatile substance. When exposed to air the sodium may explode. The sodium lamp should not be disposed of in normal the normal garbage disposal. There have been many cases of garbage trucks catching fire when the bulbs in the back broke. Sodium lamps also contain mercury. The newer LPS lamps contain less mercury than before, but this has effected performance negatively.
Inventors of HPS Lamps
Early inventors of the sodium lamp knew that with a higher pressure in the arc tube that better efficiency could be achieved. The problem was that there was no material that could stand the high pressure, high temperature, and corrosive properties of sodium.
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1964
Louden, Schmidt and Homonnay worked to create a HPS lamp at Nela Park, Ohio (A General Electric research park in Cleveland, OH). Using the new Lucalox material they figured out how to create an arc tube, evacuate the tube, and insert electrodes that would withstand the hostile conditions inside the tube. The first commercial release of the lamp was in 1964. In the 1980s GE engineers further improved the lamp life and efficiency.
Louden, Schmidt and Homonnay with a prototype light
Below: video of probably the only remaining 1960s HPS prototypes in the world. It was saved from being disposed of at the GE research lab in Niskayuna, New York.
Lamps are presented in the order of chronological development
Previous: Mercury Vapor Lamps 1901 |
Arc - Incandescent - Nernst - Neon - Mercury Vapor - Sodium Lamp - Fluorescent - Halogen - EL - LED - MH - Induction |
COMMENTS?
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Written by M.Whelan with additional research by Rick DeLair
Please contact us if you are a historian and wish to correct or improve this document.
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Sources:
The Subdivision of the Light by Unknown
'A History of Electric Light and Power' by B. Bowers
Westinghouse lamp catalogues from 1901-1903
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