Frequently Asked Questions

What is an Induction Loop System ?

How do Induction Loop Systems work ?

What are the advantages of Induction Loop Systems ?


What is an Induction Loop ?

An induction loop allows users with a telecoil equipped hearing device (switched to the T or MT position) or anyone wearing an Induction Loop Receiver to listen inductively to sound transmitted through a magnetic field without the interference of background noise.

The telecoil is familiar to many as the method used by the telephone companies to make it easier for a hearing aid user to use a telephone. The telecoil in a hearing aid picks up the sound via the magnetic field generated by the diaphragm coil in the receiver of a telephone. Our research shows that over half of the hearing aids used in the United States are equipped with telecoils. This percentage is expected to continue to rise as more consumers and audiologists become familiar with the inherent advantages of the telecoil.

Induction loop systems have been installed in locations such as churches, public halls and auditoriums, schools, lecture halls, cinemas, service counter windows, drive-thru order and pick up windows, information kiosks, offices, airports, train stations, parks, tour and guide buses, automobiles, boats, riding academies, and homes. AMPETRONIC is the world's leading designer and manufacturer of commercial grade audio frequency induction loop systems. Our systems are used in installations throughout the world.

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How do Induction Loops Work ?Simple Room Loop

It is well known that when an alternating current is passed through a wire, a magnetic field is generated around the wire. If a second wire is brought within this magnetic field, a corresponding alternating current is created within the second wire. In technical language, a current is said to be "induced" in the second wire. Hence the term "induction". This particular electromagnetic principle is the basis on which electrical motors, electrical generators and transformers operate.

An induction loop system "induces" hearing aid telecoils or an Induction Loop Receiver in the same way. An Induction Loop System consists of an amplifier and a loop. The amplifier is connected to a sound source such as a TV, a radio, a public address system or a dedicated microphone. It then amplifies this sound signal and sends it out, in the form of an alternating current, through the loop. The loop itself consists of insulated wire, one turn of which is placed around the perimeter of the room in a simple loop system. When the alternating current from the amplifier flows through the loop, a magnetic field is created within the room. The magnetic field "induces" the hearing aid telecoil or the Induction Loop Receiver.

If a hearing aid user switches to the T or MT position on their hearing aid or if an individual is wearing an Induction Loop Receiver, the telecoil in the hearing aid or Induction Loop Receiver picks up the fluctuations in the magnetic field and converts them into alternating currents once more. These are in turn amplified and converted by the hearing aid or the Induction Loop Receiver into sound. The magnetic field within the loop area is strong enough to allow the person with the hearing aid or Induction Loop Receiver to move around freely in the room and still receive the sound at a comfortable listening level.

While this principle is well known and appears straightforward, in practice only well designed constant current driven amplifiers coupled with correct loop design, can provide the pure, undistorted sound necessary to satisfy both the listeners and the regulators demands. AMPETRONIC designs and manufactures the finest, commercial quality constant current driven induction loop amplifiers available and provides technical support to ensure correct loop design.

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Advantages of an Induction Loop

In a noisy environment, or one in which reverberations and echoes are noticeable, we all find it difficult at times to hear and understand what is said. For a person with impaired hearing wearing a hearing aid, it can be almost impossible to hear and understand under such conditions. Induction Loop Systems offer the following advantages:

Hearing aids with a telecoil do not need a loop receiver / headset to receive the sound signal. This eliminates picking up and returning receivers / headsets and battery maintenance issues.

Induction Loop Systems can be used anyone without a telecoil equipped hearing aid by using an ILR2 receiver / headset or similiar. The system is useful to both the hearing disabled and those with normal hearing.

Induction Loop Systems deliver sound directly to the hearing aid in pure, undistorted form. This optimizes the benefits of hearing aids that are customized for an individual's specific hearing loss. The signal provided by an induction loop system is not affected by the distance the listener is from the sound source, nor by any interfering background noises in the room. The can significantly improve the intelligibility of speech.

Using a telecoil is inconspicuous. There is no need to call attention to a disability. This translates into much greater acceptance by those with hearing disabilities. Induction Loop Systems are much more likely to be used than either IR or FM systems.

Telecoils eliminate hygienic concerns. This overcomes a normal reluctance to putting something in one's ear that has been used in someone else's ear.

Induction Loop Systems are the only workable option in transient situations. In settings such as ticket counters, drive-thru windows, airport gates, trains, subways, and information kiosks there is no practical way to pass out the receivers / headsets required for using FM or IR systems.

An Induction Loop System can be used without others in the area being disturbed by the sound level in a sheltered or residential environment.

Induction Loop Systems accept any analog signal as input, i.e. microphones, audio, TV, mixer boards, doorbells, voice intercoms, telephone ringers and can transmit it throughout the entire looped area. Digital signal sources can be converted to an analog signal source.

Induction Loop Systems are the most cost efficient assistive listening technology.

Induction Loop Systems operate on a universal frequency. This eliminates problems inherent in operating on multiple frequencies associated with FM systems.

Induction Loop Systems are not effected by light or line site issues. This permits use in areas that are brightly lit or in direct sunlight.

AMPETRONIC Induction Loop Systems can be configured in phased arrays and low-spillover designs eliminating privacy concerns.

It is for these reasons that more attention is now being given to induction loop systems in churches, public halls and facilities, schools, theaters, cinemas, sheltered and residential accommodations, workplace settings, service counter windows and transient environments. As Social, welfare, and public health authorities become increasingly aware of the needs of the hearing disabled, and the Americans with Disabilities Acts mandates accommodating those hearing disabilities, the cost-efficient, flexible induction loop system stands out as the best assistive listening technology.

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Copyright 1999 AssistiveAudio. All rights reserved.
Information in this document is subject to change without notice.
Other products and companies referred to herein are trademarks or registered trademarks of their respective companies or mark holders.
Revised: November 12, 2002.