Home audio and video systems have changed dramatically from their earliest incarnations. Television began as a mechanical device but didn’t really catch on until electronic TVs began to hit the market and more broadcasters began signing on.
It grew more popular as it changed from tiny black-and-white screens to large color sets. And now you can buy TVs that can take up the whole wall of your living room! In February 2009, television stations in the United States will switch from analog to digital signals, encouraging people to buy converter boxes or make the move and upgrade, which means plunking down big money for new high-definition sets.
Televison may be the cornerstone of home audio and video setups, but most people need more than just a good TV. We started recording TV shows on videocassette recorders, but fewer people use them anymore. They’re all switching to digital video recorders, DVDs and Blu-ray discs. And then there’s those sophisticated component sound systems and surround sound systems that add so much character and depth to our television and movie watching.
No doubt, home audio and video equipment is very popular, but deciding on the best equipment can be a challenge. Each person has his or her own preferences that lead to very different choices. We have a whole library of home audio and video articles that will help you learn more about different technologies. Find out what’s inside a remote control. Learn the differences between plasma and LCD televisions. See how speakers work. Find out how to bend your TV schedule to suit your viewing habits, with Internet TV, the TiVo and the Slingbox. We’ll even sneak a peek at the next wave of technologies, such as ultra-high definition TV. Explore our Home Audio and Video articles to find out more.
There are few situations more terrifying than being trapped underground with no visible means of escape. Miners risk being caught in this situation every day they go to work. In the United States, the Mine Safety and Health Administration establishes guidelines and safety measures that help minimize the chance of a disaster. But sometimes that’s not enough.
According to the Bureau of Labor Statistics, the fatality rate for miners in 2007 was 24.8 per 100,000 people employed. Only the collective industries of agriculture, fishing, forestry and hunting had a higher fatality rate. Not every fatality was the result of a collapsed mine. An equipment failure or poor safety habits can also end in tragedy. Miners may encounter dangerous gases like methane as they move underground, too.
One of the biggest challenges in mine safety is communication. It’s difficult to create a network that works well underground. Most radio waves can’t penetrate rock — you need to have a line of sight between the two transmission points. That’s not feasible for most mining operations. A strong communications system underground could help reduce mining accidents and increase the effectiveness of rescue operations.
A wireless radio network would be a key component of an effective communications system. Using radio waves, miners could remain in contact with surface operations. Sensors hooked up to a wireless radio network could send back environmental information to the base of operations, alerting team leaders to potentially hazardous situations before an accident can happen. And with the right tracking system, leaders could keep tabs on where miners are within the mine. In the event of an accident, leaders could determine who was in the area at the time.
Wireless technology is pervasive — you can find hotspots in airports and coffee shops. Some cities have rolled out municipal wireless networks. You might think that every mine in the world would have them, too. But remember: Radio waves have a hard time penetrating through solid rock. When you design a wireless radio network for a mine, you have to take that into account. We’ll look at two of the most common approaches to implementing a wireless radio network in a mine.
First, we’ll focus on a system with a funny name: the leaky feeder.
