趣味英语 How Does a Remote Control Work?
Before you dismiss these stories as nothing more than old wives' tales, take a moment to consider that life a few decades ago might indeed have been more difficult than it is today. For example, decades ago your older parents and relatives couldn't simply "Google" the answer to any question they might have.
Instead, they had to do research with real books! Can you imagine? If that amazes you, you'll be really surprised by how different it was to watch television. In addition to having only a dozen channels rather than hundreds, they also had to walk across the room to turn a knob on the television set if they wanted to change channels!
Today, all you need to do is push a button on the remote control to flip back and forth between hundreds of channels. In fact, many of the things you use every day can probably be controlled remotely. From garage door openers and toy cars to lights and stereo equipment, it's easier than ever to control things from a distance.
How does all this remote control technology work? Is it magic? Nope! It's science applied to technology to make our lives easier and more convenient.
Remote control has actually been around a long time. In both World War I and World War II, radio-frequency devices were used to control boats and explosive devices remotely. Eventually, scientists would figure out how to incorporate that technology into all sorts of electronic devices.
Today, remote control devices are usually based upon one of two main types of technology: infrared (IR) technology or radio frequency (RF) technology. Let's look at how these types of technology help you control devices from afar.
When it comes to televisions and home theater devices, the dominant technology tends to be infrared. An IR remote (also called a transmitter) uses light to carry signals from the remote to the device it controls. It emits pulses of invisible infrared light that correspond to specific binary codes.
These codes represent commands, such as power on, volume up, or channel down. The controlled device (also called the receiver) decodes the infrared pulses of light into binary code that its internal microprocessor understands. Once the signal is decoded, the microprocessor executes the commands.
IR remotes use LED lights to transmit their infrared signals. This results in a few limitations of the technology. Since light is used to transmit the signal, IR remotes require line-of-sight, which means you need an open path between the transmitter and receiver. This means that IR remotes won't work through walls or around corners. They also have a limited range of about 30 feet.
Radio-frequency remotes work in a similar way. Instead of using infrared light, though, they transmit binary codes to a receiver via radio waves.
This gives RF remotes a much greater range than IR remotes. RF remotes can work at distances of 100 feet or more. This makes them useful in applications such as garage door openers and car alarms. You can also now find RF remotes being used with some modern satellite television systems.
RF remotes aren't without their own issues, however. Although range is greatly improved compared to IR remotes, interference can be an issue for RF remotes due to the large number of radio waves all around us nearly all the time. For example, wireless internet and cell phones both use radio signals.
To get around the issue of interference, many RF remotes only transmit at specific frequencies. They can also embed digital address codes in the radio signals to ensure that a receiver only responds to the correct radio signals.
a rounded projection or protuberance——knob
at or from or to a great distance; far——afar
an area in which something acts or operates or has power or control——range
(of an electronic device) operating or operated by means of radio or infrared signals——remote
cease to consider; put out of consideration——dismiss
give careful consideration to——consider
systematic investigation to establish facts——research
having a wavelength just greater than that of the red end of the visible light spectrum but less than that of microwaves——infrared
set that receives radio or tv signals——receiver
man-made equipment that orbits around the earth or the moon——satellite
of doubtful authenticity, although widely circulated as being true——apocryphal
suited to your comfort or purpose or needs——convenient
include or contain; have as a component——incorporate
exercising influence or control——dominant
device used to broadcast radio or tv signals——transmitter
integrated circuit semiconductor chip that performs the bulk of the processing and controls the parts of a system——microprocessor
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