Assistive Listening and alerting (signaling) devices are used with or without an individual's hearing aid or cochlear implant, to help an individual hear in challenging hearing environments.
Assistive Listening or alerting systems are systems that help a group of people hear in difficult hearing enviroments, usually but not always in large venues such as theaters, concert halls, and lecture halls.
The technology used in listening or signaling systems may be wired or wireless and be catagorized as Frequency modulated (FM), Infrared (IR), Bluetooth, or electromagnetic, such as used in a "hearing loop".
Alerting (signaling) devices may utilize loud sound, flashing or strobe lights, or vibrations to alert the user to a sound or danger they otherwise may not hear.
Assistive Listening Devices (ALD's) and Assistive Listening Systems (ALS's) often use the telecoil in a the users hearing aid or cochliear Implant.