What are the different types of Assistive Listening Devices?
ALDs utilize different technologies. Typically, they are wireless or wired. Wireless ALDs make use of radio frequencies, light rays, or magnetic inductive energy to transmit sound. Hardwired ones use direct electrical connection to transmit the auditory signal. Each system has special features, capabilities, advantages, and disadvan-tages. Three ALD systems-FM, Soundfield Amplification, and Induction Loop Systems-will be discussed. Frequency Modulated (FM) Systems: An FM system is a wireless, portable battery-operated device that uses radio transmission to send auditory signals, i.e. speech, from a transmitter to a receiver. With most FM systems, the instructor wears a lavelier microphone connected to a body-worn transmitter. The student wears the FM receiver unit clipped to his/her clothing. The FM receiver can also be connected to the student’s hearing aid via an induction neckloop system or direct audio input cables. Special FM cables are also available for cochlear implant users. W
