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If Your Hearing Aids Are Not Enough...
Get A Helper
A Presentation by Ron Vickery

Narrator:  Many people report that even when using powerful and sophisticated hearing aids, they are not sufficient in all listening situations. The Telecoil makes it possible to use a hearing aid with Assistive Listening Systems and Devices.

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Thanks for inviting me to this meeting, Ron, but...
   What is a Telecoil?
I thought you would never ask <G>... A Telecoil is a small induction coil inside a hearing aid. It is an optional feature on some hearing aids and standard on others.
 It is actuated, or selected, with the "T-Switch".  As an analogy, think of a T-Switch as a selector switch like on home stereos. Those switches select between tuners, tape players, CD players, and auxiliary devices. The T-Switch selects either the hearing aid internal microphone or the induction coil, and by selecting the induction coil, a large variety of Assistive Devices can be used. So we ought to call the T-Switch the AD Switch, or ALD switch, or ALS switch, or maybe the mode switch.
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That's easy to see, but how does it work?

It works just great!!  Oh, you wanted a technical answer!

An induction coil is just one half of a transformer. Alternating electric current flows in the primary coil of a transformer, setting up an electromagnetic field. The field induces a alternating current in the secondary coil of the transformer. The voltage and current from the secondary may be higher or lower than the primary, depending on how the transformer is made. So, an induction coil in a hearing aid is the secondary of a very loosely coupled transformer. The primary may be the coil inside a telephone handset, or it could be a neckloop, a silhouette, or a room size induction loop.
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 But how does that make the sound better?
  It doesn't by itself. I was just talking about how the telecoil gets electrical signals into the hearing aid. Whether it will be better sound depends on where the signal is coming from. I think they will talk about that in the meeting.
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All wireline phones that you can buy now days are required to be hearing aid compatible. However existing phones may not be HAC, and people report that some phones are too weak. The audio induction loop is a big loop that goes around the circumference of the listening area. A Neckloop is just a smaller version of an audio induction loop and it is worn around the neck. The silhouette is an even smaller version and it fits right up next to the hearing aid. The last item on the list above represents interference from extraneous sources - we don't want to hear the radiation from these things and they cause a problem for some people. The neckloop and silhouette are called induction coupling devices because they are driven by some other device and provide a coupling of the device and the hearing aid.
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Now I'm going to talk about the types of Assistive Devices that can be coupled to the hearing aid by way of the telecoil.  Yeah!!  

Far out, man.



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The neckloop provides coupling to these things.

The man in this picture is hard of hearing, and he really wants to hear what she is saying. He gets her  voice directly, as indicated by the red arrow, but he also gets her voice almost as good but delayed slightly from the walls of the room.
Another factor affecting understanding is that some sounds in speech do not carry as good over distance and those sounds get masked out. A third factor is extraneous noise, represented by the noise arrow. Noise comes from air conditioning, overhead projectors, and of course, other people talking. These three factors contribute to a difficult listening situation.
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If he was using a FM receiver with a neckloop and his hearing aids were set for ALD mode, (T-Switch) and she was using a FM transmitter, then the listening effect would be as if he moved closer to her. Actually moving closer might be a better solution, but that  is not always possible. The noise level from 
reverberation and extraneous sources has been reduced. This is just one example. The same principle applies using any type of Assistive Listening System or Device. His microphone on his hearing aid is usually turned off and the only source of sound comes from a microphone very close to the person speaking.
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That was interesting, but could you run that by me again?
Maybe a drawing will help.
The dashed line indicates a direct connection, and the squiggly red line means a wireless communication path. This shows two examples.

Mic--Transmitter ~~~~> Receiver--Neckloop ~~~~> Telecoil/Hearing Aid

                        Mic--Amplifier--Neckloop ~~~~> Telecoil/Hearing Aid
The next page shows a real life example that we see everyday on TV.

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Visualize a TV personality interviewing people on a NYC sidewalk outside the studio. We never see the camera but we know there must be one, maybe two or three. The camera could be a few feet from the interview with  modern zoom lenses. But what about the microphone? He does not leave the mic in the studio, or even have it attached to the camera. He carries a mic and holds it close to the interviewee. I think the man above is using a wireless mic, but it doesn't make any difference except for convenience. I remember "the man on the street" radio interviews, and they used a corded mic like shown above. The important thing is that the broadcast media knows it has to get good sound and that means "on mic", or close up sound, rather than "off mic" sound. The same is true for hard of hearing people using hearing aids. The hearing aid has a microphone, so it has to be close to the sound source. Assistive Devices coupled through the telecoil makes it possible to get "on mic" sound when it is not physically easy to actually get close to the sound. It doesn't matter if the Assistive Device uses radio, infrared, or is hardwired, although each system has it's pros and cons.
One more thing that I haven't mentioned is the "direct connect" type of connection. This is called Direct Audio Input, or DAI. It bypasses the telecoil with a patch cord that connects a remote mic or other Assistive Device directly to the amplifier in the hearing aid. I haven't said much about the big room sized audio induction loops either. I think that should be the subject of another presentation.
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You've got me interested... where can I get more information?
There are some really good WEB sites that talk about these things. I'll put up a link to my links page, then how about you and me use our Tele-Coils to call on the Tele-phone for a Tele Supreme Pizza??
 my links page
-- End --
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