Table IV.

Assistive listening devices: devices used by hearing impaired individuals to improve hearing ability in difficult listening environments (e.g., background noise) and/or for safety precautions.

Type	Description
FM System	This system transmits audio signals via radio waves. The speaker wears a transmitter/microphone that transmits the signal wirelessly to earphones/hearing aids attached to a receiver. This system is worn to improve audibility in difficult listening situations (e.g., classrooms, restaurants, meetings).
Audio streamers	These systems wirelessly connect hearing aids to TVs, MP3 players, computers, and Bluetooth-enabled phones and devices. Some are also compatible with FM systems. The signal from the connected device (TV, computer, phone, etc.) is sent wirelessly and directly to the hearing aids.
Contralateral Routing of Signal (CROS)	A behind-the-ear hearing aid designed specifically for patients diagnosed with single-sided deafness. The CROS is fit on the poor ear, which transmits sound to a hearing aid worn on the better hearing ear. This device helps patients with single-sided deafness better localize sound and understand speech in noisy environments.
Telecommunication	A variety of options are available to help the hearing impaired use the telephone such as alerting lights, amplified phones, telecoil circuitry, and text telephone (TTY).
Infrared systems	This system uses an invisible light beam that transmits sound from the speaker to earphones or a neck loop (if hearing aids have a telecoil option).
Induction loop systems	An induction loop wire is installed in the periphery of a room and connects to a microphone worn by the speaker. The signal from the microphone generates a current in the loop wire, which creates an electromagnetic signal that can be received by the telecoil inside a hearing aid. These systems are most common in large group areas such as classrooms, churches, performing arts centers, airports, etc. but can be purchased for individual use.
Alerting systems	Systems that use flashing lights, loud sounds, or vibrations to alert the person of environmental sounds (e.g., telephone, alarms, doorbell, baby crying).