102 | EQUALITY ACT & ASSISTANCE PRODUCTS | INDUCTION LOOP SYSTEMS t: 0845 884 7000 | f: 0845 884 6000 | w: www.channelsafety.co.uk | @channelsafety | EDITION 7 SIZE OF AREA REQUIRING COVERAGE CHIL PRODUCT Counters, desks, tables & other small areas up to 1.2m2 PL1 portable loop kit, ML1/ K counter loop kit, CHIL102C counter loop kit VL1/ B1 vehicle loop kit Rooms up to 50m2 CHIL102L/R/S small room kits DL50/K domestic loop kit Rooms up to 200m2 (11 x 11m) AK RANGE loop kits CHIL200E amplifier Rooms up to 200m2 (14 x 14m) CHIL200/2 professional loop amplifier Rooms up to 500m2 (22 x 22m) CHIL500/2 professional loop amplifier Rooms up to 1000m2 (30 x 30m) CHIL1000/2 professional loop amplifier What is an Audio-Frequency Induction Loop System? Audio-frequency induction loop systems allow hearing impaired people to hear more clearly. Most hearing aids have a‘T’or‘MT’switch which allows them to pick up the electromagnetic field generated by an induction loop system. The hearing aid converts this signal into a sound suited to its user’s specific hearing requirements. Any person with a hearing aid positioned within or near the loop can hear the loop signal by switching their hearing aid to the correct position, allowing them to participate more effectively in general conversation, order goods or services, listen to public performances, etc. An induction loop system therefore comprises the following main elements:- The audio source - typically a microphone, television or radio (or a combination of these). The Induction Loop Amplifier The loop - typically a single turn of wire usually run around the perimeter of the room or a special counter loop fixed to the underside of a table. The receiver(s) - any hearing aid with a‘T’or‘MT’switch or a specially designed loop listening device. In addition to the many routine benefits for hearing aid users, induction loop systems can also be used for other limited area broadcasting applications such as museum‘walk through’ guided tours and surveillance talkback systems. The Main Elements Of An Audio-Frequency Induction Loop System Some induction loop systems may require additional audio sources such as multiple microphone or line level inputs. To facilitate this, many CHIL range amplifiers include an‘Outreach’socket which allows the connection of multiple inputs via a range of specially designed single gang audio connector plates. How Does An Induction Loop System Work? Audio-frequency induction loop systems do not use radio frequencies; they operate at audio frequencies. The signal from an audio source is fed into an induction loop amplifier, which amplifies and sets the signal level in the same way as a conventional amplifier. The amplified signal, instead of going to a loudspeaker, is fed to a closed loop of cable that is normally placed around the perimeter of the room. Employing a constant current amplifier ensures the current is maintained at the set level whilst providing a flat frequency response without the need for equalisation circuitry. The current flowing through the loop generates a magnetic field that radiates in the space around the loop cable. Any lines of magnetic flux that pass through the telecoil in a receiver, such as a hearing aid, will generate a current in the coil that is then converted back to audio and fed into the listener’s ear. It is important to remember that the magnetic field will‘bleed’outside the perimeter of the loop and therefore a loop system cannot be considered confidential. Why We Have Induction Loop Systems In normal use, hearing aids utilise a microphone for amplifying localised speech. Whilst this is effective for local conversations/quiet environments, it is less effective for listening to speech or music at a distance or in front of a security screen at a ticket counter. This is because the hearing aid’s microphone also picks up any background noise in the room and unwanted speech from other conversations. An induction loop system works by moving the required sound closer to the hearing aid via the hearing aid’s telecoil which is activated by turning it to the‘T’or‘MT’ position. As telecoils are fitted as standard to most hearing aids (over 90% are said to have the‘T’position) induction loop systems can be considered cost-effective compared to other hearing assistance systems. Infrared systems, for example, require special receivers, the cost and maintenance of which must be met by the service provider. Many modern hearing aids do not just amplify all frequencies equally; they are tailored to suit the user’s hearing problem and amplify different bands by different amounts. This gives maximum intelligibility, so the user has the best chance of understanding what is said. Which induction loop system should I use? The CHIL range of induction loop equipment is one of the most comprehensive in the UK. It comprises a huge range of amplifiers, microphones, connector plates and test equipment covering virtually every conceivable AFILS application. Before deciding which induction loop system to use, you first need to ascertain the size of the area to be covered in square metres (m2). Bear in mind it may not be necessary to cover the whole of the area, for example in a church only the pews may require coverage. To calculate the size of the area in square metres, multiply the length by the width. For example, a room 6m x 6m in size would equal 36m2. (The coverage provided by an AFILS amplifier is also quoted in square metres). The chart below, and information in the rest of this section, will help you select the best CHIL Range product(s) for the job. Guide to selecting your Induction Loop System Designed to meet or exceed the requirements of BS7594 and EN60118-4 when correctly installed, all of the amplifiers in the CHIL range offer excellent intelligibility, true current mode amplification, phantom power (for electret microphones) and full compatibility with the‘outreach plate’audio input extension system (except the PL1, VL1 and DL50). Many are also available in kit format for ease of specification, purchase and installation. HEARING AID INDUCTION LOOP AMPLIFIER THE LOOP AUDIO SOURCE AUDIO SOURCE The main elements of an induction loop system