Cordless headphones receive sound through a built-in radio-frequency receiver, which eliminates the need for a wire through which to transfer the sound. A radio transmitter plugs into the headphone jack of the audio device. It converts the audio-signal output to a radio frequency and transmits the radio frequency over the air. Within a certain range, the receiver picks up the radio waves and converts the signal into audio information.
After the signal is converted back into audio information, the headphone speakers play the information into the person's ears just like a set of headphones with a cord. The radio transmitter can be plugged into any standard-size headphone jack in an audio device, such as a computer, television, stereo speaker, smartphone or any other electronic device. The radio receiver is usually built into the base of the headphones. Some wireless headphones work by using infrared signals, instead of radio waves, to transfer the audio information. Devices using Bluetooth to transfer the data use radio transmissions. Cordless headphones can be rechargeable or use batteries. The lack of a wire restricts the person's movement less while wearing the headphones, although to keep receiving the sound the person must stay within the range of the transmitter.