It is expect that nearly every household in the United States has at least one radio. The invention of the radio was dependent upon two previous discoveries: the electromagnet and telegraph.
The electromagnet was discovered in 1825. This discovery opened the doors to global communication! Five years later, Joseph Henry successfully transmitted an electric current via wire which was stretched over a mile and which caused an electromagnet to trigger the sounding of a bell. Thus, the electric telegraph was born. One of the most recognizable names associated with the telegraph is Samuel Morse who is most notable for the series of dots (brief sound) and dashes (more sustained sound) which was used to transmit messages by alphabet code (thus known as Morse Code). Telegraph became the sole means of rapid long distance communication until 1877 and the invention of the telephone.
Batteries are interesting, aren`t they Used by the general consumer, they are small, but powerfully packed instruments which produce power used for many cameras, alarm clocks, radios, and other devices. What makes this power production possible In the case of the telephone and it`s early design and use, batteries produced the essential source of power for the electromagnet.
Batteries have two ends to which one is assigned a `+` or positive, and the other a `-` or negative. When a battery operated device is switched on, the electrons which are produced by the batteries, quickly move from the negative side to the positive side of the batteries. Something was needed to interrupt this rapid flow of electrons or find the batteries totally expended in a brief time. In order to accomplish this, a wire is often inserted between the positive and negative terminals and a `load`, such as a radio, creating a small magnetic field in the wire. The electromagnetic waves which are present now, have the capability to transmit sounds (speech, music, and so on) as well as visual images undetected by sight through the air.
There are several scientists who must be mentioned as essential to the telephone as it is known to most of us. Mahlon Loomis created wireless telegraph. Guglielmo Marconi, proved the possibility of radio communication. In 1985 Marconi, transmitted and received a radio signal. Using the Morse alphabet, he sent the first wireless signal which was transmitted across the English Channel and in due time, he was able to receive the Morse letter S which began in England and reached Newfoundland which became the beginning of transatlantic radiotelegraphy (1902).
Wireless signals gained far reaching use as a means of communication for rescue work when an accident or disaster occurred at sea. In 1899 the United States Army began utilize wireless communication which originated from a lightship off Fire Island. The US Navy was about two years behind the Army in utilizing wireless telegraphy.
In 1903, President Roosevelt (Theodore) and King Edward VII communicated via this new and improving technology. The well known Robert Perry, using radiotelegraphy, conveyed the message that he had `found the Pole`.
The first AM radio entered the world of telecommunication in the early 1900`s. This device made the use of somewhat weak waves possible for communication. This was the time when the term `radio`, as we know today for radio devices, began to be used.
It is believed that in December 23, 1900, professor Reginald Aubrey Fessenden was the first person to successfully transmit human voice by radio waves. By 1915, speech was first sent across the United States beginning in New York City and sent to San Francisco. Somewhat later, transmission occurred across the Atlantic Ocean from Arlington, Virginia, to Paris at the Eiffel Tower.
It is truly fascinating all the scientists and the physics theories that led to the invention of the radio. Marconi, Alexander Popov, Oliver Lodge, Fessenden and many others, have all made important contributions to an invention that made the world so different, that most likely none of them would envision. The radio era was born.
This article is under GNU FDL license and can be distributed without any previous authorization from the author. However the author's name and all the URLs (links) mentioned in the article and biography must be kept.
http://www.articleco.com/Article/A-Brief-History-Of-The-Radio/50842
Monday, September 3, 2007
Home Theater Design: Where to Place Your Speaker System
Whether investing a large amount of your savings or a small part of your budget on your home theater, your speaker placement will play a big role in the sound quality and sonic performance in your home theater room.
The instructions that come with your speakers will give you recommendation for where to place them within a room but below are a few things to consider as you begin setting up your new home theater speakers.
CENTER CHANNEL SPEAKER
This speakers main purpose is to anchor sounds on-screen, like dialogue.
Tips for placement of the center channel speaker:
1. Center it directly above or below your television.
2. If you place it above the television, the front edge of the speaker should line up precisely with the front edge of the television. This will cut down on any kind of sound bouncing around inside the television cabinet.
3. The tweeter of this particular speaker should be at the same height as the tweeters of the front speakers. If you can accomplish this to within 24 inches, that will allow for the best sound quality.
4. The front speakers and this particular speaker should be spaced the same distance away from your planned listening position.
FRONT SPEAKERS: BOTH LEFT AND RIGHT
These speakers have two distinct purposes. They reproduce stereo music sound while also handling a movies soundtrack.
Tips for placement of the front speakers:
1. Find your optimal listening position. Now space the two front speakers at points in the room that are equal is distance to that position, with one to the left and one to the right. The front right, front left and center channel speakers should all be approximately the same distance from where you are sitting, with the tweeters of each directed at your ears. Dont just eyeball this and get an approximate distance, as even an inch variation in the distance of the speakers can make a noticeable difference in your home audio systems sound quality.
2. These speakers tweeters should be even to your ear level when seated in the optimal listening position. Smaller home theater speakers can be mounted on the wall or placed on a speaker stand. Floor standing speakers normally have this covered in their design.
SURROUND SPEAKERS
The purpose of the surround speakers is to provide low and high level sound from other parts of the room, creating a movie theater feel in your home theater. The surround speaker placement will depend on the size of your home theater, the shape of the room, and the space needed for the actual speakers. Be creative and experiment with the placement of these particular speakers throughout the room.
Tips for placement of the surround speakers:
1. Place the primary pair to the right and to the left of your optimal listening position. This can be done in line with your position or just behind it. When placement to the side is impossible, or when you have a surround system with more than two surround speakers, you may wish to place the speakers behind the listening position, with the sound being directed toward the front of the room.
2. These speakers should be placed at approximately ear level when you are in a standing position.
3. Experiment with the aiming of these speakers when mounted on the walls. Sometimes good results can be achieved when you point them up at the ceiling or back at the rear corners of the room.
SUBWOOFER
A home theater subwoofer provides your home audio system with all the low bass frequencies needed for a movie theater, surround sound experience. However, it is one of the least difficult to position. In most cases, you can position your home theater subwoofer anywhere in your home theater and still get good results.
There is no one perfect placement for any given home theater speaker. No two rooms acoustics will be the same, all speakers will have various sonic characteristics, and no two ears will hear any given sound identically. This doesnt mean you will never achieve the best sound quality from your home audio system. All it means is take the advice given and modify it when you actually install your home theater speakers to accommodate your specific needs.
http://www.articleco.com/Article/Home-Theater-Design--Where-to-Place-Your-Speaker-System/54030
The instructions that come with your speakers will give you recommendation for where to place them within a room but below are a few things to consider as you begin setting up your new home theater speakers.
CENTER CHANNEL SPEAKER
This speakers main purpose is to anchor sounds on-screen, like dialogue.
Tips for placement of the center channel speaker:
1. Center it directly above or below your television.
2. If you place it above the television, the front edge of the speaker should line up precisely with the front edge of the television. This will cut down on any kind of sound bouncing around inside the television cabinet.
3. The tweeter of this particular speaker should be at the same height as the tweeters of the front speakers. If you can accomplish this to within 24 inches, that will allow for the best sound quality.
4. The front speakers and this particular speaker should be spaced the same distance away from your planned listening position.
FRONT SPEAKERS: BOTH LEFT AND RIGHT
These speakers have two distinct purposes. They reproduce stereo music sound while also handling a movies soundtrack.
Tips for placement of the front speakers:
1. Find your optimal listening position. Now space the two front speakers at points in the room that are equal is distance to that position, with one to the left and one to the right. The front right, front left and center channel speakers should all be approximately the same distance from where you are sitting, with the tweeters of each directed at your ears. Dont just eyeball this and get an approximate distance, as even an inch variation in the distance of the speakers can make a noticeable difference in your home audio systems sound quality.
2. These speakers tweeters should be even to your ear level when seated in the optimal listening position. Smaller home theater speakers can be mounted on the wall or placed on a speaker stand. Floor standing speakers normally have this covered in their design.
SURROUND SPEAKERS
The purpose of the surround speakers is to provide low and high level sound from other parts of the room, creating a movie theater feel in your home theater. The surround speaker placement will depend on the size of your home theater, the shape of the room, and the space needed for the actual speakers. Be creative and experiment with the placement of these particular speakers throughout the room.
Tips for placement of the surround speakers:
1. Place the primary pair to the right and to the left of your optimal listening position. This can be done in line with your position or just behind it. When placement to the side is impossible, or when you have a surround system with more than two surround speakers, you may wish to place the speakers behind the listening position, with the sound being directed toward the front of the room.
2. These speakers should be placed at approximately ear level when you are in a standing position.
3. Experiment with the aiming of these speakers when mounted on the walls. Sometimes good results can be achieved when you point them up at the ceiling or back at the rear corners of the room.
SUBWOOFER
A home theater subwoofer provides your home audio system with all the low bass frequencies needed for a movie theater, surround sound experience. However, it is one of the least difficult to position. In most cases, you can position your home theater subwoofer anywhere in your home theater and still get good results.
There is no one perfect placement for any given home theater speaker. No two rooms acoustics will be the same, all speakers will have various sonic characteristics, and no two ears will hear any given sound identically. This doesnt mean you will never achieve the best sound quality from your home audio system. All it means is take the advice given and modify it when you actually install your home theater speakers to accommodate your specific needs.
http://www.articleco.com/Article/Home-Theater-Design--Where-to-Place-Your-Speaker-System/54030
Choosing a Home Theater DVD Player for your Home Theater
With all the new developments in audio-visual equipment on the market, it is hard to keep up with it all. However, there are some basics you should be aware of when looking for certain items, like your home theater DVD player.
The first question you may be asking is Why do I need DVDs and a DVD player at all My VHS works just fine. Well, the reasons are many. A home theater DVD:
- has a much sharper and clearer picture than video cassettes
- has superior sound quality to any VHS tape
- is less prone to having background noise
- allows you to see movies in wide screen or full screen
- allows you to watch movies in multiple languages or with subtitles
- has extras, like bloopers, movie trailers and sometimes interviews
- can be used as a CD player as well (make sure it is CDR/CDRW compatible)
Once youve decide to purchase a home theater DVD player, you will need to educate yourself on what type of player you need for your specific home theater system. What follows will give you an outline of what to look for when you go to purchase your new player.
Here are some things you should look for in a quality DVD player:
AUDIO OUTPUTS
Every home theater DVD will have analog stereo outputs. This just means that it has the capability of being hooked into any two-channel amplifier.
However, with the increased use of Dolby Digital Surround Sound, many of the newest, most cutting edge players will have six extra audio outputs. This will allow for the decoded 5.1 signal associated with Dolby Digital.
There are a couple of ways that the audio signal can get to your home theater receiver. Most have a digital connection, which can be accomplished through a coaxial or an optical connection. Your newest home theater DVD players and receivers oftentimes have both connections, but it never hurts to look and make sure you are getting just what you need.
VIDEO OUTPUTS
Most home theater DVD players have several video output connections that you can choose from. The one most commonly found is composite output. Most of the televisions available today have composite input and are therefore compatible with such a player.
If you are looking for a better picture, be sure to look for a television and DVD player with S-Video. This is considered a step up from composite. If you are using a television you currently own with your new DVD player and it has S-Video, be sure to use this connection.
There are two higher quality outputs available: component and rgb. If you are buying a whole home theater system all at once, including a home theater DVD player and possibly a home theater LCD flat panel television, you will want to look for equipment that will be compatible and work together as an audio-visual unit. Look for outputs on the player and inputs on the television.
ZONING CONSIDERATIONS
The entire world is divided into zones. The US can be found in zone 1, the UK can be found is zone 2, Southeast and East Asia can be found in zone 3, etc. Not all DVDs purchased can be played on all home theater DVD players, if you get one created for a specific zone.
When buying a new home DVD theater system, what you should look carefully for is a player that will play movies from any zone. Most on the market today have been modified so that they will play any and all DVDs, not matter what zone they were created for.
The actual sound and picture quality between DVD players can vary. Visit a local audio video retailer to listen and view the quality and features of the players available. It is also a good idea to read product reviews for various models of home theater DVD players before you buy, to see which brands and models are getting the better ratings and why.
All DVD players are not the same but the ultimate result is a dynamic, exciting new feature to your home theater system.
http://www.articleco.com/Article/Choosing-a-Home-Theater-DVD-Player-for-your-Home-Theater/54052
The first question you may be asking is Why do I need DVDs and a DVD player at all My VHS works just fine. Well, the reasons are many. A home theater DVD:
- has a much sharper and clearer picture than video cassettes
- has superior sound quality to any VHS tape
- is less prone to having background noise
- allows you to see movies in wide screen or full screen
- allows you to watch movies in multiple languages or with subtitles
- has extras, like bloopers, movie trailers and sometimes interviews
- can be used as a CD player as well (make sure it is CDR/CDRW compatible)
Once youve decide to purchase a home theater DVD player, you will need to educate yourself on what type of player you need for your specific home theater system. What follows will give you an outline of what to look for when you go to purchase your new player.
Here are some things you should look for in a quality DVD player:
AUDIO OUTPUTS
Every home theater DVD will have analog stereo outputs. This just means that it has the capability of being hooked into any two-channel amplifier.
However, with the increased use of Dolby Digital Surround Sound, many of the newest, most cutting edge players will have six extra audio outputs. This will allow for the decoded 5.1 signal associated with Dolby Digital.
There are a couple of ways that the audio signal can get to your home theater receiver. Most have a digital connection, which can be accomplished through a coaxial or an optical connection. Your newest home theater DVD players and receivers oftentimes have both connections, but it never hurts to look and make sure you are getting just what you need.
VIDEO OUTPUTS
Most home theater DVD players have several video output connections that you can choose from. The one most commonly found is composite output. Most of the televisions available today have composite input and are therefore compatible with such a player.
If you are looking for a better picture, be sure to look for a television and DVD player with S-Video. This is considered a step up from composite. If you are using a television you currently own with your new DVD player and it has S-Video, be sure to use this connection.
There are two higher quality outputs available: component and rgb. If you are buying a whole home theater system all at once, including a home theater DVD player and possibly a home theater LCD flat panel television, you will want to look for equipment that will be compatible and work together as an audio-visual unit. Look for outputs on the player and inputs on the television.
ZONING CONSIDERATIONS
The entire world is divided into zones. The US can be found in zone 1, the UK can be found is zone 2, Southeast and East Asia can be found in zone 3, etc. Not all DVDs purchased can be played on all home theater DVD players, if you get one created for a specific zone.
When buying a new home DVD theater system, what you should look carefully for is a player that will play movies from any zone. Most on the market today have been modified so that they will play any and all DVDs, not matter what zone they were created for.
The actual sound and picture quality between DVD players can vary. Visit a local audio video retailer to listen and view the quality and features of the players available. It is also a good idea to read product reviews for various models of home theater DVD players before you buy, to see which brands and models are getting the better ratings and why.
All DVD players are not the same but the ultimate result is a dynamic, exciting new feature to your home theater system.
http://www.articleco.com/Article/Choosing-a-Home-Theater-DVD-Player-for-your-Home-Theater/54052
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