What Is HDMI®

HDMI® (High-Definition Multimedia Interface) is an interface standard used for audiovisual equipment such as high-definition television and home theater systems. With 19 wires wrapped in a single cable that resembles a USB wire, HDMI® is able to carry a bandwidth of 5 Gbps (gigabits per second). This is more than twice the bandwidth needed to transmit multi-channel audio and video, future-proofing HDMI® for some time to come. This and several other factors make HDMI® much more desirable than its predecessors, component video, S-Video and composite video. 

HDMI® is an uncompressed, all-digital signal, while the aforementioned interfaces are all analog. With an analog interface, a clean digital source is translated into less precise analog, sent to the television, then converted back to a digital signal to display on screen. At each translation, the digital signal loses integrity, resulting in some distortion of picture quality. HDMI® preserves the source signal, eliminating analog conversion to deliver the sharpest, richest picture possible. 

Previous video interfaces required separate audio cables, with the vast majority of people using standard RCA L/R analog audio jacks. HDMI®, with its abundant bandwidth and speed, carries not only video but also up to eight digital audio channels for uncompromised surround-sound. It replaces the tangle of wires behind the system with a single cable, greatly simplifying the entire setup process of the home theater system while delivering top tier performance. 

Though standard HDMI® or "Type A" has 19 wires, "Type B" will have 29 wires. The latter is targeted for the motion picture industry and other professional applications. Both varieties are "Intelligent HDMI®," referring to the built-in capability for HDMI®-enabled components to talk to each other via the interface. Auxiliary information can provide all-in-one remote functionality and other interoperable features not possible in previous interface technologies.

HDMI® supports standard video formats, enhanced video and high-definition. It is also backwards compatible with DVI (Digital Video Interface). High-end graphics cards featuring a DVI port can connect to a HDMI® interface via a DVI/HDMI® cable. This is simply a cable with a DVI connector on one end and a HDMI® connector on the other. As a rule, HDMI® cables should not run longer than 15 feet (5 meters), or degradation of the signal could occur.

As of 2005, many high-end television sets were sold with at least one HDMI® interface. Some experts advise that two HDMI® interfaces will provide more flexibility, and for those who want to connect a game console, three might serve better. Multiple interfaces will become common on digital TVs as the industry incorporates HDMI® interfaces into more peripheral components.

What Are Transducers

Transducers are electric or electronic devices that transform energy from one manifestation into another. Most people, when they think of transducers, think specifically of devices that perform this transformation to gather or transfer information. In reality, however, anything that converts energy can be considered a transducer.

Found Throughout Everyday Life

Common transducers that detect or transmit information include microphones, Geiger meters, pressure sensors, thermometers and antennae. A microphone, for example, converts sound waves that strike its diaphragm into an analogous electrical signal that can be transmitted over wires. A pressure sensor turns the physical force being exerted on the sensing apparatus into an analog reading that can be easily represented. Many people think of a transducer as being some sort of technical device, but they can be found in many places throughout everyday life.

Most transducers have an inverse that allows for the energy to be returned to its original form. Audio cassettes, for example, are created by using a transducer to turn the electrical signal from the microphone pick-up — which went through a transducer to convert the sound waves into an electrical signal — into magnetic fluctuations on the tape head. These magnetic fluctuations are then read and converted by another transducer — in this case, the stereo system — to be turned back into an electrical signal. This signal is then fed by wire to speakers that act as yet another transducer to turn the electrical signal back into audio waves. 

Other transducers turn one type of energy into another form, not to measure something in the external environment or to communicate information, but rather to make use of that energy in a more productive manner. A light bulb, for example, converts electrical energy into visible light. Electric motors are another common form of electromechanical transducer, converting electrical energy into kinetic energy to perform a mechanical task. The inverse of an electric motor — a generator — also is a transducer, turning kinetic energy into electrical energy that can then be used by other devices.

Efficiency

As in all energy conversions, some energy is lost when transducers operate. The efficiency of a transducer is found by comparing the total energy put into it to the total energy coming out of the system. Some transducers are very efficient, and others are extraordinarily inefficient. 

A radio antenna is one example of an efficient transducer. The antenna acts as a transducer to turn radio frequency power into an electromagnetic field. When the antenna is operating well, this process can be more than 80 percent efficient. Most electrical motors, by contrast, are less than 50 percent efficient. A common light bulb, because of the amount of energy that is lost as heat, is less than 10 percent efficient.

What is a DVD-ROM

A Digital Versatile Disc — Read Only Memory, or DVD-ROM, is a media storage disk that closely resembles a CD or compact disk. The major difference is that the DVD-ROM is formatted to hold far more data. A CD commonly has a capacity of 650 megabytes, while the smallest capacity DVD can store about seven times more data, or 4.38 gigabytes (GB). 

There are various kinds of DVDs, but the DVD-ROM refers to a read-only disc, or a disc that cannot be written over. If you purchase a DVD movie from the local video store, you have a good example of a DVD-ROM. Blank DVDs with designations like "DVD-R" and "DVD+R" are formatted, recordable DVDs. The —R and +R refer to competing format standards, but both will record movies, audio or other data.

A DVD-ROM encodes data in the form of a spiraling trail of pits and lands separated by mere nanometers. The trail starts at the center of the DVD-ROM and winds around countless times until it reaches the outer edge. In the case of a double layer disk, the trail continues on a second layer of material. If the disc is also double-sided, the trail of pits and lands extends to side two. 

A laser beam in the DVD player tracks the beam as the disc spins, while a special device reads the intensity of the reflection as it bounces off the pits and lands. The reflective variance gets translated to bits of data which form bytes. Hence, DVDs, including the DVD-ROM, can vary in capacity as follows:

1. Single-sided single-layer disc — 4.38 GB
2. Single-sided double-layer disc — 7.95 GB
3. Double-sided single-layer disc — 8.75 GB
4. Double-sided double-layer disc — 15.9 GB

The DVD-ROM has replaced the videocassette, being far more efficient and superior in all respects. For one, a DVD-ROM stores data in digital form, while the videocassette uses less precise analog technology. A DVD-ROM, under normal conditions, remains error free and consistent, regardless of the amount of times it is viewed, while a video cassette stretches with wear and eventually needs replacement. The DVD-ROM can also hold more information in a higher format, and one can skip to specific scenes without the need for fast-forwarding or rewinding. Finally, the DVD-ROM is much more compact and easier to store, and DVD players can double as CD players.

If purchasing a DVD player, be sure to get one that can play all DVD-ROM formats, including double-sided, double-layered discs. For home theater systems look for models equipped with a 192 kilohertz (kHz), 24-bit digital/analog converter (DAC) for true Dolby theater quality. By comparison, standard DVD players use 96 kHz, 24-bit DACs. This is still a big improvement over CDs, however, which use 44.1 kHz, 16-bit sampling to produce audio. For this reason, people are moving towards DVDs to store music. An audio DVD can hold just over an hour of multi-channel music at 192 kHz, the highest bit rate; about two hours at 96 kHz; and close to seven hours at the standard CD sampling rate of 44.1 kHz. 

While cassettes, videocassettes and laser diskc have become legacy technologies, the DVD-ROM appears to be here to stay. Recordable DVDs are available wherever music and movies are sold, including department stores, office supply chains and discount marts.

What Is CDMA

CDMA stands for Code Division Multiple Access. It is a technique used for digital communication, and wireless technology in particular, that involves multiplexing. Whereas conventional communication systems use constant frequencies, CDMA uses multiple access, or multiplexing. Accomplished through the specific type known as spread spectrum in this case, multiplexing uses varied frequencies to transmit audio signals. This, coupled with code division, which requires a certain code to send and receive the frequency, further protects CDMA communications from interference.

Radio systems, one of the earliest forms of telecommunication, required users to communicate on distinct frequencies. Frequency Division Multiple Access (FDMA), one form of early wireless communication, only allowed users to operate on a single frequency. When tuning in to a radio to get sound, for instance, the listener must select one frequency or another, and must tune the frequency to filter out noise in the spectrum. Another form of early radio communication was Time Division Multiple Access (TDMA). In this case, users could not share a frequency, and each user had to coordinate his or her turn on that frequency in order to communicate.

Both FDMA and TDMA posed restrictions for early users, particularly the military. As early as World War II, militaries recognized the high value in using wireless technology to communicate across vast distances. Military communication units did not always have the time to wait their turn to transmit sound, or to find the right frequency. 

Some telecommunication systems allowed military communication units to transmit sound into the same spectrum their adversaries used. Military signals needed a unique identification through a distinct code to avoid interference from enemy communication. The receiver of that message on the other end could then retrieve the message based on its unique code in the spectrum. 

Just as the radio moved from military use to commercial use, so too was the case with the wireless technology. CDMA became the early choice for personal communication because it could allow multiple users to communicate within the spectrum, avoiding interference or blocking among users. In 1999, CDMA became the standard technology for the telecommunications industry for its growing wireless systems. Since there are large numbers of users in the system communicating at the same time, code division ensures that each user’s signal remains separate in the spectrum.

What Is a Power Inverter

A power inverter is a device that converts DC power (also known as direct current), to standard AC power (alternating current). Inverters are used to operate electrical equipment from the power produced by a car or boat battery or renewable energy sources, like solar panels or wind turbines. DC power is what batteries store, while AC power is what most electrical appliances need to run so an inverter is necessary to convert the power into a usable form. For example, when a cell phone is plugged into a car cigarette lighter to recharge, it supplies DC power; this must be converted to the required AC power by a power inverter to charge the phone.

How Inverters Work

DC power is steady and continuous, with an electrical charge that flows in only one direction. When the output of DC power is represented on a graph, the result would be a straight line. AC power, on the other hand, flows back and forth in alternating directions so that, when represented on a graph, it appears as a sine wave, with smooth and regular peaks and valleys. A power inverter uses electronic circuits to cause the DC power flow to change directions, making it alternate like AC power. These oscillations are rough and tend to create a square waveform rather than a rounded one, so filters are required to smooth out the wave, allowing it to be used by more electronic devices.

Most electronic devices require AC power to work correctly because they are designed to be plugged into a standard wall outlet, which supplies AC power. These devices need a specific amount of low, regulated voltage in order to operate. AC power is easier to step up or down, or change from one voltage to another, than DC and easier to regulate. In many cases, when a power inverter is in use, DC power is being converted to AC power, which is then stepped down and turned back into DC power inside the device.

Types of Inverters

Most modern power inverters produce either modified square (or modified sine) waves, or pure sine (or true sine) waves. Modified square wave inverters don't provide the smooth peaks and valleys that AC power from a home's electrical outlet does, but it can deliver power that is consistent and efficient enough to run most devices. This type of inverter is relatively inexpensive, and probably the most popular type.

Pure sine wave inverters are the most expensive, but they also deliver the smoothest and most even wave output. Any device will run on a pure sine wave, but some sensitive equipment, like certain medical equipment and variable speed or rechargeable tools, requires this type of inverter to operate correctly. Radios, for example, work better with pure sine wave inverters because the modified square wave inverter's less-smooth waves disrupt the radio's reception, causing static and other noise.

Inverter Uses

Basic power inverters are often small, rectangular devices that plug directly into the cigarette lighter or DC outlet on the dashboard of a car or other vehicle. This size inverter is usually sufficient to run a laptop, a small television, a portable DVD player, or similar equipment. These devices don’t draw a lot of power and can be used continuously while the vehicle is running; they may even be used for a half-hour to an hour while the engine is off, such as while camping or during a power outage at home.

Other power inverters come with jumper-like cables so they can be connected directly to a battery. This type is required to run more powerful equipment, such as power tools at a remote work site or a larger TV. Inverters can also be hard-wired into a battery to make them easier to use with larger pieces of equipment.

Larger inverters are used to convert solar or wind energy into AC power that can be used in a home. Called a grid-tie inverter, this device links into the utility grid to allow power to be delivered along the same wires that supply energy from a electric utility. It even allows any excess power produced to be fed back into the grid, where it can be sold to the utility company.

Inverter Capacity

Different models of power inverters vary in how many watts of power they can supply. The capacity of an inverter should equal the total number of watts required by each device, plus at least a 50% addition to account for peaks or spikes in the power draw. For example, if a DVD player draws 100 watts and a small TV another 100 watts, a minimum 300-watt inverter is recommended. Getting an inverter with more capacity than what is immediately needed is a good idea for many people, as it means that different or new devices can be added without the need for a new power inverter.

Safety

When using a power inverter continuously inside a vehicle that is not turned on, the engine should be started at least once an hour for 10 to 15 minutes to keep the battery from running down. A vehicle should never be started in a closed garage, as the carbon monoxide in the exhaust is fatal. 

Power inverters should only be used with batteries that are in good condition and fully charged. A weak battery will be drained easily if demand is too high. If used in a car, this could leave a driver stranded, so the battery's condition should be checked before using an inverter in a stationary vehicle. If the inverter is being used while the vehicle is running, as in the case of a road trip, there should be no problem with the extra draw as long as the battery is in good condition.

Working with large batteries can be dangerous, and when not done properly, can result in serious injury. Improper use of a power inverter can even lead to electrocution. For safety reasons, someone attempting to hook an inverter directly to a battery should be sure to read and follow any and all safety precautions listed in the inverter's instruction booklet.

It is important for people to always use a power inverter that is rated high enough for the device that needs to be run. If a heavy-duty power saw is plugged into a cigarette lighter, for example, the lightweight inverter might overheat and cause a fire in the dashboard. Adapters that allow more outlets than the unit is designed to accommodate should be avoided, and proper ventilation around the inverter is required to prevent overheating.

What is a Hydrogen Bomb

A hydrogen bomb is, by far, the most destructive weapon that mankind has ever invented. It is the most powerful type of nuclear bomb, as much as 25,000 times the yield of the nuclear bombs dropped on Hiroshima and Nagasaki, Japan. Unlike conventional atom bombs (also known as A-bombs), which release energy by fissioning (breaking apart) heavy atomic nuclei like uranium and plutonium, a hydrogen bomb releases energy by fusing together light nuclei like tritium or deuterium, converting even more matter into energy. When Truman authorized the dropping of the A-bomb on Hiroshima and Nagasaki, he said that the weapons used the same power that the Sun did, but that wasn't actually true -- the Sun uses nuclear fusion, not nuclear fission. Thus, a hydrogen bomb really does release the power that fuels the Sun.

The largest nuclear bombs, and the backbone of the nuclear arsenal of the United States and Russia, are hydrogen bombs. These bombs work using a two-stage design whereby a fission bomb "primary" is detonated using the conventional implosion method, which then compresses a fusion fuel "secondary" and ignites a uranium "spark plug" which fissions and subjects the fusion fuel to the heat necessary to begin a chain reaction -- about 20 million degrees F. The light nuclei fuse together into heavier elements, releasing tremendous energy from the strong nuclear force that binds their constituent particles together.

As a result of using fusion rather than fission, the bomb yield is much higher. In fission bombs, approximately 0.1% of the mass of the fuel is converted directly into energy, while in fusion bombs, this ratio is slightly improved, on the order of 0.3%. The first time the principle of a hydrogen bomb was tested was on 9 May 1951 by the United States military, during the George shot of Operation Greenhouse at the Pacific Proving Grounds. Most of the yield of this test came from fission fuel, but it tested the idea that a fission bomb could be used as a stepping stone to something even more destructive. A similar test, Item, took place on 25 May 1951.

The first true hydrogen bomb test, Ivy Mike, was on 1 November 1952, detonated at Enewetak Atoll in the Pacific, as part of Operation Ivy. The bomb exploded with a force equivalent to 10.4 megatons of TNT (over 450 times more powerful than the atomic bomb dropped on Nagasaki during WWII). Using liquid deuterium as fuel, this hydrogen bomb required 18 tonnes of refrigeration equipment to keep the deuterium in liquid form. A later test, Castle Bravo, used solid lithium deuteride instead, decreasing the weight of the device and making it a practical weapon. The Castle Bravo shot is the most powerful nuclear weapon ever tested by the United States, with a yield of 15 megatons.

Today, all of humanity is still put at risk by a nuclear winter initiated by hydrogen bombs.

How Can I Play the Music on my Computer Through my Stereo

Music files have revolutionized the way people listen to and archive music. Soft MP3 players, or software designed to play music files, have made it easy and convenient to build ad-hoc playlists for any occasion or mood. Although programmable compact disk (CD) players allowed some flexibility to create playlists, the ease of clicking to add tunes to a software interface makes other forms of programming feel downright archaic and restrictive by comparison. It’s no wonder then that people want the option of using soft MP3 players to listen to music files through the main stereo system or entertainment center. Luckily, it’s an easy thing to do, and it can be done wired or wirelessly.

The most common and least expensive way to route music from your computer to your stereo system is to run an RCA audio cable from the sound card on the computer to the stereo receiver. All sound cards are made with at least one Line Out jack, used to power computer speakers. The jack is normally a 3.5mm mini phone plug. An inexpensive adapter that features a 3.5mm stereo jack at one end, and two female RCA jacks at the other will work well here. This will connect to a standard RCA stereo cable. The opposite end of the cable will plug into the stereo or surround sound receiver. Here you’ll need an available Audio Line In RCA port, which may be marked Aux for auxiliary. 

After the connection is made, set the volume down before powering up the receiver. Change the receiver mode to auxiliary (rather than tuner, CD, DVD, TV, etc.), and slowly turn the volume up. You may need to boost the volume control of soft MP3 player as well. 

Advanced sound cards might also have other Line Out options, such as Digital Out. The instructions are the same, substituting a digital cable for the RCA cable. The receiver will also need a Digital Audio-In port.

Though wired methods are inexpensive, they have the disadvantage of requiring a physical cable to run from the computer to the stereo system. If the computer is a desktop located in a different room from the stereo or entertainment center, this can be impractical. A laptop provides a good mobile medium for music libraries, as it can be set rather close to the stereo system to simplify things and keep wires out of walkways.

When hard wiring your music connection isn’t practical, another method is to go wireless. In this case a small transmitter is connected to the Line Out port of the sound card, and a matching receiver is connected to the Audio Line In port of the receiver. Music from the computer is silently broadcast via radio waves from the transmitter to the receiver. The receiver interprets the radio signals and translates them back into an audible signal to play through the speakers of the entertainment center. 

Wireless stereo transmitters vary in design and pricing and a few models are expressly designed for iTunes music. Others include composite video ports to send not just audio, but video signals between the computer and entertainment center. Cables might be included or sold separately. For more information check your local electronics stores or your favorite online retailers.