Radio Remote Controls
Radio-frequency (RF) remote controls are very common. Garage-door openers, car-alarm fobs and radio-controlled toys have always used radio remotes, and the technology is starting to show up in other applications, too. They're still pretty rare in home-theater devices (with the exception of RF extenders, which we'll discuss on the next page), but you will find RF remotes controlling certain satellite-TV receivers and high-end stereo systems. You'll also find Bluetooth-based remotes that control laptops and smartphones. (See How Bluetooth Works to learn about this radio technology.)
Instead of sending out light signals, an RF remote transmits radio waves that correspond to the binary command for the button you're pushing. A radio receiver on the controlled device receives the signal and decodes it. The problem with RF remotes is the sheer number of radio signals flying through the air at any given time. Cell phones, walkie-talkies, WiFi setups and cordless phones are all transmitting radio signals at varying frequencies. RF remotes address the interference issue by transmitting at specific radio frequencies and by embedding digital address codes in the radio signal. This lets the radio receiver on the intended device know when to respond to the signal and when to ignore it. To learn more about the technology of radio-frequency remotes, check out How Remote Entry Works.
The greatest advantage to radio-frequency remotes is their range: They can transmit up to 100 feet from the receiver (the range for Bluetooth is shorter), and radio signals can go through walls. This benefit is why you'll now find IR/RF remotes for home-theater components. These remotes use RF-to-IR converters to extend the range of an infrared remote.
In the next section, we'll talk about RF extenders and other special remote-control features.