OT Hearing Aid user and the telephone.

"John J Armstrong" wrote in message
...
On Thu, 23 Oct 2008 22:46:29 +0100, "Bill Wright"
wrote:


"Paul Martin" wrote in message
.. .
In article ,
David wrote:
with maybe
a radio lav for the minister.

Our vicar could certainly make use of a radio lav.

Bill


Well there was this, which may not have been reported your side the
Tweed:

http://news.scotsman.com/weirdoddand...wee.2776566.jp

Ahh that's lovely. It must have remined the congregation that even the vicar
is made of mortal flesh!

Bill

In message , Paul Martin
writes
In article ,
J. P. Gilliver (John) wrote:
In message , Paul Martin
writes

The instance I'm thinking of has the dimmer switches at the front of
the church, and the lighting wiring at ceiling level all the way to the
back of the church. Triac-based dimmers clip each edge of the mains
waveform even when fully on, producing magnetic fields in the wiring at
50Hz, 150Hz, 300Hz, 450Hz, etc. Hearing aids will probably roll off
anything under 100Hz anyway to avoid picking up mains hum, but the
higher harmonics will get through.

I was under the impression that modern dimmers used zero-crossing
switching (presumably involving microprocessor, or at least something a
bit more complicated than the conventional). Though this won't help
existing systems.

Ah, but how do you switch on and off the AC current in proportion even
with zero-crossing switching but without generating too much heat in
the controller? These are domestic-type dimmer switches, and triacs are
probably involved.

By only switching on one cycle in three, or three cycles in four, or
whatever. The original dimmer switches used to switch on every cycle,
but an adjustable distance through it - which generated horrendous
interference. Plenty of these are still around. Some - I had thought it
all, but I may be wrong there - modern ones do their best only to switch
at (or near) zero-crossings, which generates less.

Both the old type and the new are at any instant either off or on, so
don't generate too much heat in the controller, provided the on
resistance is low enough. Neither sort work too well with non-resistive
loads - they tend to make fluorescents (old or new type) flicker badly
and can shorten their life, and if used for inductive loads can destroy
the dimmer.
--
J. P. Gilliver. UMRA: 1960/1985 MB++G.5AL(+++)IS-P--Ch+(p)Ar+T[?]H+Sh0!:`)DNAf
Lada for sale - see www.autotrader.co.uk

"Don't worry about people stealing your ideas. If your ideas are any good,
you'll have to ram them down people's throats." - Howard Aiken

"Dave Liquorice" wrote in message
ll.net...
On Fri, 24 Oct 2008 09:38:56 -0700, Tonyatk wrote:

Many thanks for all the respondants. But i was looking for a system for
one room in my house. I wondered if any one has such a system bought or
DIY, and can offer some addvice.

I'm losing track of the thread... You want a small loop system for one
room in your house? A complete kit is available from CPC for £115.50 (inc
VAT).

http://cpc.farnell.com/DP28063

They also have a range of other amps and bits look under: Audio, Video &
TV PA, Disco & Musical Equipment Assistive Hearing Products.

If you have a spare mono audio amplifier of say 20 to 30W RMS that could
be a DIY solution with a bit of multicore cable(*) laid around the room
and wired to form a few turns. What you will be missing is the compressor
that dedicated loop amps have to reduce the dynamic range. Loops need to
be driven to work well, small signals produce low loop currents thus don't
couple so well to the receiver.

(*) Choose something without any twists or pairs, alarm cable say or flat
telephone extension cable.

--
Cheers
Dave.




Hi Dave
Thanks for the lead . I will look into what you say. just what I was looking
for.

Best regards

Tony

The message et
from "Dave Liquorice" contains these words:

====snip====

If you have a spare mono audio amplifier of say 20 to 30W RMS that could
be a DIY solution with a bit of multicore cable(*) laid around the room
and wired to form a few turns. What you will be missing is the compressor
that dedicated loop amps have to reduce the dynamic range. Loops need to
be driven to work well, small signals produce low loop currents thus don't
couple so well to the receiver.

(*) Choose something without any twists or pairs, alarm cable say or flat
telephone extension cable.

(*) It doesn't matter if, as I am assuming, you mean to loop a
multicore cable and effectively connect each wire in series to create
your multi turn loop. The same current will be flowing in the same
direction along each wire, so no cancellation effects are involved.

A ten pair cable will allow you to generate 20 ampere turns from a 1
amp source and the presence of twists between the seperate 'turns' will
have almost zero effect at audio frequencies and not that much of an
effect at higher frequencies until you start to consider frequencies
measured in tens of MHz and above (where you'll tend to connect them in
parallel anyway to reduce the impedance of your loop, turning your
single turn loop into one that uses the Litz effect to reduce I2R
losses).

HTH

--
Regards, John.

Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

The message
from "J. P. Gilliver (John)" contains these words:

====snip====

I was under the impression that modern dimmers used zero-crossing
switching (presumably involving microprocessor, or at least something a
bit more complicated than the conventional). Though this won't help
existing systems.

Your thinking of heater element control and similar low frequency
variable duty cycle controllers. Unfortunately, this technique is
inappropriate for light dimmers (you'd get horrific flicker using
zero-crossing switch control methodology here).

HTH

--
Regards, John.

Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

The message
from Paul Martin contains these words:

====snip====

Ah, but how do you switch on and off the AC current in proportion even
with zero-crossing switching but without generating too much heat in
the controller? These are domestic-type dimmer switches, and triacs are
probably involved.

He was thinking of a very low interference method of using thyristor
control of heating elements and similar slow response devices or devices
that are only required to be active for short periods of time.

The 'Zero-Crossing (current)' method eliminates the high energy
switching transients normally associated with the phase delay switching
control technique used by incandescent lighting dimmers.

The 'Zero-Crossing (current)' method blocks complete full cycles of the
mains waveform and allows complete full cycles in a variable ratio to
achieve the desired average level over periods ranging from two cycles
to several hundred (dependind on how fine a control is needed), varying
the duty cycle between blocked and passed complete cycles of mains
_current_. The resulting flicker from this control technique makes it
totally inappropriate for lighting control.

HTH

--
Regards, John.

Please remove the "ohggcyht" before replying.
The address has been munged to reject Spam-bots.

"Tonyatk" wrote in message
et...
While my good wife sits in her chair with the volume at her level.

And which chair does your bad wife sit in, since you needed to qualify that
you were talking about your good wife? ;-)

"Mortimer" wrote in message
et...
"Tonyatk" wrote in message
et...
While my good wife sits in her chair with the volume at her level.

And which chair does your bad wife sit in, since you needed to qualify
that you were talking about your good wife? ;-)

He might not have a bad wife. He might have an indifferent one. Mine's been
indifferent for some time now.

Bill

"Tonyatk" wrote in message
et...

"David" wrote in message
...


"Owain" wrote in message
...
David wrote:
Talking loops in a Church if she uses the 'T' loop she only gets the
voice and not the music so does not use the loop there. Sounds to me
only speech passes through it and not the music.

That's the fault of the church for not putting a music feed through.
They should have a separate mix for the inductive loop to enable music
and the congregation singing to go into the loop.

Yes I would think that the wireless tie mic. could well be the one
feeding the loop.
She does have no problems listening to normal PA which we are of course
listening too.
I would think the Church PA guys have plenty on without a second mixer
for this loop to operator as well. The PA system and the computer to
put words on to a screen via a projector.

--
Regards,
David

Please reply to News Group


Many thanks for all the respondants. But i was looking for a system for
one room in my house. I wondered if any one has such a system bought or
DIY, and can offer some addvice.

Regards Tony



For anyone that's interested.

I constructed an inductive loop system for my chair.
A loop about 8 foot long out of telephone wire 8 wires connected in series
about 4 ohms and AF amp of 12 watts( which I picked up at radio ham show).
This did the trick. I can now sit in my chair and hear everything with my
hearing aid. While my good wife sits in her chair with the volume at her
level. This makes a very happy spouse which all in all can't be bad.

Cost of this project £6 total this includes the box and all the connectors
and sockets

Tonyatk

On Tue, 25 Nov 2008 18:41:54 -0000, Tonyatk
wrote:


"Tonyatk" wrote in message
et...


Many thanks for all the respondants. But i was looking for a system for
one room in my house. I wondered if any one has such a system bought or
DIY, and can offer some addvice.

Regards Tony



I remember seeing a white panel about one foot square on the counter of a
local shop which turned out to be an induction loop system.

Cheers

James.