The impulse is usually transmitted through a wire to the headphones. With wireless SkullCandy headphones, monster beats, the impulse is transmitted through signals that travel through the air. This eliminates the need for a transmission cord. Wireless headphones use different signal mediums for the transmission of sound waves. These include Bluetooth, radio, or infrared. Radio and Bluetooth signals work in a similar way, but radio has greater coverage than Bluetooth. SkullCandy deals in various products targeting action sports, outdoor activities, and general consumer markets. In the consumer market, they have established a large following with their brand of SkullCandy headphones, which are suitable for people with an action sports lifestyle. Another style of headphones clips the earpiece around the base of the outer ear. Other styles include in-ear headphones and under-the-chin headphones. These in-ear headphones are often bundled with iPods and other MP3 players and can simply be placed in a pocket. Another type of headphones, which are larger than in-ear headphones, sit on the ear and include an elastic frame that either sits on the head or wraps around the neck. The majority of today's headphones are so-called dynamic headphones. Dynamic refers to the type of transducer used. Another kind are static headphones. Static headphones are rather expensive and require specific headphone amplifiers. Another type of wireless headphones are digital wireless headphones. This type of headphones, such as Amphony headphones, will encode the audio before transmission, which prevents any audio distortion during the transmission and ensures high reliability against interference.