How Does Remote Control Work?

Remote Controls Have Existed Since World War II

Few people know that the first remote controls in the world were developed for military purposes. Remote controls using radio frequency appeared during World War I to guide German naval ships to collide with Allied vessels.

By World War II, remote controls were used to detonate bombs. After the war, this remarkable technology continued to be improved to serve human life effectively. Today, it can be said that almost everyone has used a remote control to operate some device.

Initially, remote controls utilized Radio Frequency (RF) technology, and later, Infrared (IR) technology was applied to remote controls. Currently, we use both types of remote controls in our daily lives. Thus, what are the differences in the structure, features, and limitations of each type?

Infrared Remote Controls (IR)

Today, this type of remote control plays a “dominant” role in most household devices. An IR remote control consists of basic components housed in a digital cable junction box: buttons, an integrated circuit board, contact knobs, and a light-emitting diode (LED).

The fundamental principle of this type of remote control is to use infrared light from the electromagnetic spectrum, which is invisible to the human eye, to transmit signals to the device being controlled. It acts as a signal transmitter, emitting bursts of infrared light carrying a specific binary code. When a button is pressed, a series of operations are triggered, allowing the controlled devices to execute the command associated with that button.

Diagram of a remote control. (Image: HowStuffWorks)

The process works as follows: First, when a button like “Increase Volume” is pressed, it touches the contact knob below and completes a circuit to increase the volume on the circuit board. Integrated circuits can detect specific circuits for each button. These circuits then send signals to the LED located at the front. From there, the LED emits a series of light pulses containing binary codes (composed of sequences of 1s and 0s) corresponding to the “increase volume” command. This command code includes multiple sub-codes such as start, increase volume, device address code, and stops when the button is released.

On the receiving end, the device consists of a infrared signal receiver located at the front to easily receive signals from the remote control. After verifying that the address code originates from the correct remote, it decodes the light pulses into binary data for the device’s microprocessor to understand and execute the corresponding commands.

Currently, we use IR remote controls for most household items like televisions, stereo systems, air conditioners, etc. They are very durable; however, they have limitations related to the straight-line nature of light transmission. Thus, IR remote controls have an operational range of about 10 meters and cannot transmit through walls or around corners. They work best when pointed directly at or near the receiver of the device being controlled.

Moreover, infrared light sources are abundant, such as sunlight, fluorescent bulbs, and even from the human body, which can cause signal interference for IR remotes. To avoid this phenomenon, filters are installed in the receiving components to only detect specific wavelengths or frequencies of infrared light suitable for them, blocking light at other wavelengths to minimize interference as much as possible.

Radio Frequency Remote Controls (RF)

This is the first type of remote control, which continues to play an important and widespread role in life today. While IR remotes are typically used indoors, RF remotes are employed for many outdoor devices, such as garage door openers, remote-controlled electronics, and even satellite controls and systems for laptops and smartphones.

Various remote controls. (Source: Internet)

This type of control also uses a similar principle to infrared controls, but instead of sending light signals, it transmits radio waves corresponding to binary commands. The radio frequency receiver on the controlled device receives and decodes the signal. Compared to IR controls, the biggest advantage of RF remote controls is their wide transmission range, able to operate from over 30 meters away and can even penetrate walls and glass.

However, it also has limitations because radio signals are present in the environment due to hundreds of devices using radio signals at different frequencies. To avoid interference, people transmit at special frequencies and embed the digital address code of the receiving device within the radio signals. This allows the radio receiver on the device to respond accurately to the corresponding signal.

Currently, both types of remote controls are widely applied in everyday life. They are often integrated into universal remote controls that can operate multiple devices simultaneously or execute a series of commands with the press of a single button. Additionally, advancements have been made to develop extenders that convert radio signals into infrared pulses to extend the operational range of household devices…