Sentry’s HW702 pack of two headphones with a transmitter is great to use both indoors and outdoors for listening to music or TV without disturbing others. Headphone features a built-in FM radio with a reception up to 100 feet. Use around home, at the office or outdoors with TV, iPhone, iPod, MP3, CD, DVD players and more. Features: on/off button; frequency range: 20Hz-20kHz, impedance: 16 Ohms, sensitivity: 110db; Four foot cord length with 3.5mm plug. Transmitter uses two AAA batteries (not included); headphones use four AAA batteries (not included).