What is a Telecoil?
The telecoil is a small induction pick-up coil which can be placed inside a hearing aid. The telecoil is also known as a T-coil, or T-switch. When activated, the telecoil permits coupling of the personal hearing aid to sources of electromagnetic energy including a telephone and assistive listening devices and systems.
When used with the telephone, the telecoil permits a direct communication between the hearing aid and the phone without the interference of acoustic feedback. The term "hearing aid compatible" refers to a telephone's ability to inductively couple to a telecoil equipped hearing aid. But telecoils are not just for telephones. Telecoils permit the receiver of any assistive listening device and system to inductively couple to the personal hearing aid via an induction neckloop or silhouette. This coupling allows the ALD to supplement the personal hearing aids rather than to take the place of the hearing aids. With induction loop assistive devices the hearing aid's telecoil IS the receiver for that type of technology and therefore it has built- in accessibility. Users of non-telecoil equipped hearing aids have to remove their hearing aids and wear headphones or earbuds in order to use the receiver of an assistive listening device or system. This may work fine for someone with a mild or moderate hearing loss, however, a severely hearing impaired person may not find the ALD receiver alone to be powerful enough and therefore cannot benefit from the assistive device.
Most behind-the-ear hearing aids are routinely manufactured with telecoils, however, this circuit must be requested and added to in-the-ear hearing instruments. Not all telecoils are created equal and can differ widely in sensitivity even in otherwise comparable hearing instruments. Potential users should evaluate the telecoil feature of a hearing instrument equally with the acoustic performance of the aid. The selection of a programmable telecoil will allow the audiologist to modify the performance of the telecoil to
Acoustic and Inductive Coupling Methods
Assistive Listening Devices
Assistive listening devices (ALDs) may be used by individuals with all degrees of hearing loss whether or not they also use personal hearing aids. How the ALD receiver should be coupled to the user's ears depends on several factors including degree of hearing loss, personal preference, comfort, and presence or absence of the telecoil circuit if personal hearing aids are also worn. Facilities providing large area ALDs should make a variety of the following coupling methods available in order to appropriately accommodate users of their systems.
Earphone Headsets or Earbuds
Earphone headsets or earbuds are examples of acoustic coupling methods that work fine with mild to moderate hearing losses and must be used when the user's personal hearing aids have no telecoils or the user has no hearing aids. Earphones are typically binaural and may or may not be stereo. Some earphones headsets are built into the receiver such as with an infrared under-the-chin receiver. Earbuds may be monaural (one ear) or binaural (both ears). Both headsets and earbuds have washable or replaceable earpads, an important feature for large area ALDs with multiple users.
Induction Neckloops
Induction neckloops are a type of inductive coupling desired by users of in-the-ear and behind-the-ear telecoil equipped hearing instruments. For moderately, moderately-severe, and severely hearing impaired individuals, inductive coupling to the hearing aid's telecoil is essential to get the most benefit from the ALD. The induction neckloop is a coil of wire worn around the neck that creates an induction field exactly like larger induction loop technology. The neckloop plugs into the ALD receiver and converts the signal into electromagnetic energy which is picked up by the hearing aid's telecoil.
Induction Silhouettes
Induction silhouettes are another type of inductive coupling for users of telecoil equipped hearing aids both in-the-ear and behind-the-ear styles. A silhouette, which is shaped like a hearing aid, sits behind the ear and houses tiny coils of wire which convert the signal from the ALD into electromagnetic energy which is then received by the hearing aid's telecoil. Like the induction neckloop, the silhouette is essential for users of ALDs. Users of behind-the-ear hearing instruments often prefer the greater proximity of the silhouette to the hearing aid's telecoil circuit.