Basics
Wireless headphones are a convenient device that allows a user to listen to music, TV, movies and other programming without disturbing others. Since they don't use a hard-wired connection, wireless headphones allow the user additional comfort and mobility. Wireless headphones consist of two separate parts: the transmitter and the headset.
Connections
Since the headphones do not have wired inputs they do not connect directly to the stereo. Instead, the transmitter is connected to either the headphone jack or one of the available audio outputs on the stereo. The transmitter receives the audio signal from the stereo and in turn sends it to the headphones.
Transmission
Wireless headphones use one of two methods of transmission: infrared or radio waves. Infrared headphones require a direct line of sight with the transmitter without any walls, furniture or other objects between the headphones and transmitter. This is because infrared systems are light-based; just the way you can't shine a flashlight through a wall, infrared cannot be transmitted through a solid object. Radio waves are less directional than infrared and don't require a direct line of sight. They can be picked up from a variety of angles and often in other rooms. However, other devices that operate on similar radio frequencies, such as cordless phones, can interfere with headphone reception. With both systems, the audio signal that is processed in the stereo is simply sent out through the air and then picked up by a receiver built into the headset.
Dynamic Drivers
Once the signal has been received by the headphones, the current from the signal is sent to the dynamic drivers in each headphone. A dynamic driver is essentially the same as a speaker driver. Alternating current creates a changing magnetic orientation in the electromagnetic voice coil. The changing polarity of the coil causes it to repel and attract with a stationary magnet, essentially vibrating rapidly in tune to the music. When the coil moves, it moves an attached diaphragm and sends vibrations (sound waves) into the listener's ears.
Tags: audio signal, direct line, direct line sight, line sight, require direct, require direct line
