infra red headsets for AD
 

Hi, I was just wondering, does anyone know anything about the system
installed in Theatres and cinemas to give audio description?I'm not
interested in the DVD interface and all that stuff. I'd like to know how the
transmission is done. I assume its analogue of some sort, judging by the way
the noise level can vary if you move.
The reason I'm interested is that a user of these is looking for a device to
be able to test the headsets are working when they are giving them to the
customers. Being a big multi screen cinema with only 1 equipped screen, it
is irritating to the blind customers to get in the cinema, and then find
when the film starts, the headsets battery is knackered or the headset is
not working for some reason. What seems to be needed is a device like a
remote control, which puts out a tone on the infra red system used so the
set can be tested at the box office. After all, if it is not working in the
cinema, and you are not with a sighted person, getting the headset swapped
is going to be awkward and would mean missing the film or part of it.

Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!

infra red headsets for AD
 

"Brian Gaff"

Hi, I was just wondering, does anyone know anything about the system
installed in Theatres and cinemas to give audio description?I'm not
interested in the DVD interface and all that stuff. I'd like to know how
the transmission is done. I assume its analogue of some sort, judging by
the way the noise level can vary if you move.
The reason I'm interested is that a user of these is looking for a device
to be able to test the headsets are working when they are giving them to
the customers. Being a big multi screen cinema with only 1 equipped
screen, it is irritating to the blind customers to get in the cinema, and
then find when the film starts, the headsets battery is knackered or the
headset is not working for some reason. What seems to be needed is a
device like a remote control, which puts out a tone on the infra red
system used so the set can be tested at the box office. After all, if it
is not working in the cinema, and you are not with a sighted person,
getting the headset swapped is going to be awkward and would mean missing
the film or part of it.


** The best idea is to find an IR transmitter intended for domestic use that
is a close enough match to the system used in the cinema. Then it could be
used for testing purposes.

Gotta know all about the cinema system to do that.

Or get very lucky.


....... Phil

infra red headsets for AD
 

Its the system used I'd like to find out about though.

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"Phil Allison" wrote in message
...

"Brian Gaff"

Hi, I was just wondering, does anyone know anything about the system
installed in Theatres and cinemas to give audio description?I'm not
interested in the DVD interface and all that stuff. I'd like to know how
the transmission is done. I assume its analogue of some sort, judging by
the way the noise level can vary if you move.
The reason I'm interested is that a user of these is looking for a device
to be able to test the headsets are working when they are giving them to
the customers. Being a big multi screen cinema with only 1 equipped
screen, it is irritating to the blind customers to get in the cinema, and
then find when the film starts, the headsets battery is knackered or the
headset is not working for some reason. What seems to be needed is a
device like a remote control, which puts out a tone on the infra red
system used so the set can be tested at the box office. After all, if it
is not working in the cinema, and you are not with a sighted person,
getting the headset swapped is going to be awkward and would mean missing
the film or part of it.


** The best idea is to find an IR transmitter intended for domestic use
that is a close enough match to the system used in the cinema. Then it
could be used for testing purposes.

Gotta know all about the cinema system to do that.

Or get very lucky.


...... Phil

infra red headsets for AD
 

"Brian Gaf = Top Posting **** Head "


Its the system used I'd like to find out about though.


** You seem to have missed that I actually answered that Q already.

There is NO one IR system in use in cinemas etc.

YOU have to find out about the ONE use in the cinema in question

- ie brand and model.

Capice ?????

**** Head.



...... Phil

infra red headsets for AD
 

Hmm, it is difficult wading through bottom posting when you are blind, must
have missed a bit, but you would have thought they would have standardised
by now.
Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Phil Allison" wrote in message
...

"Brian Gaf = Top Posting **** Head "


Its the system used I'd like to find out about though.


** You seem to have missed that I actually answered that Q already.

There is NO one IR system in use in cinemas etc.

YOU have to find out about the ONE use in the cinema in question

- ie brand and model.

Capice ?????

**** Head.



..... Phil

infra red headsets for AD
 

"Brian Gaff"
Hmm, it is difficult wading through bottom posting when you are blind,
must have missed a bit, but you would have thought they would have
standardised by now.


** On another newsgroup I frequent - top posters are regularly told off
BECAUSE there is a blind person using the group. I thought you guys would
have standardised by now........

Far as IR transmitters go, most use frequency modulation of the LEDs
output - not the frequency of the light of course - but the rate at which
the LED is pulsed on and off. There is a carrier frequency ( two in the
case of stereo ) and this frequency is modulated up and down to follow the
audio signal voltage at any moment.

The receiver's circuitry is very much like an FM broadcast receiver, except
the"antenna" is a photo diode.

With the old Sennheiser system popular in the 80s and 90s, carrier
frequencies were in the hundreds of kHz.

Modern domestic IR headphone systems use carrier frequencies in the low MHz,
ie 2.3MHz and 2.8 MHz being one pair for Left and Right.

However, your cinema may well be using a mono IR system, use an odd-ball
carrier frequency or even use PPM ( pulse position modulation) instead of
FM.

With such systems, there is a strong motive to NOT standardise cos that
prevents the use of competing products.



...... Phil