Instead of using sound frequencies, infrared technology uses invisible light energy called the infrared light spectrum to deliver sound from a transmitter to the hard of hearing or deafened person. The hard of hearing person wears a special receiver or headset which works in conjunction with a loop or a T-switch in his/her hearing aid. The infrared signal will not transmit to the listener through walls or when the signal is interrupted by a moving object or person. Infarered systems are suitable for listening in both large and small groups, while watching TV, listening to the radio, in meetings or other public venues. Both FM and infrared systems are available as personal listening devices or may be provided in public venues such as meeting rooms, lecture halls, places of worship, or theatres.