Listen Technologies LA-140-WH, LA-140-GY User Manual

Listen IR Divisible (Air) Wall Tech Note

Using Listen IR Products in Divisible (Air) Wall Applications

Don’t miss a single sound.

Venues

• Hotel Ballrooms

• Convention Space

• Places of Worship

• Other Venues

• Assistive Listening

• Language Interpretation

• Government handicap

Applications

compliance (USA-ADA)

Listen Product Types Used

• Stationary IR

• Digital IR

Overview

This tech note covers the technology required to design a wireless assistive listening and/or language interpretation system for multiple room divisible (air) wall rooms. In this application, the number and size of rooms changes on an as needed basis. Each new room must provide its own wireless listening/language interpretations system no matter what the

conguration.

Example:

The ABC Convention Center has a congurable ballroom system that accommodates up to eight different rooms (see diagram 1). The rooms must be able to be divided into any of the possible congurations. For example, the room must be

capable of eight separate rooms, one large room, two medium size rooms (A-D and E-H), etc.

A E

B F

C G

D H

Diagram 1. Example of an eight room air wall system. The ABC Convention Center requires that any

combination of rooms be accommodated.

The core wireless transmission technology to be used is infrared (IR). Wireless FM (RF) technology is difcult to use in this

application because of possible interference between the many channels in the area and because the listener would be required to change to the appropriate broadcast channel. A basic requirement this example above is that the listener only needs to turn the receiver on and adjust the volume.

IR oers the following advantages:

It is secure. This signal is kept within the room.

All users can use the exact same receiver without changing channels.

An innite number of rooms can be employed.

The system can be used both for assistive listening and for language interpretation

Listen Technologies Corporation • 14912 Heritagecrest Way • Bluffdale • Utah 84065-4818 U.S.A.

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Listen IR Divisible (Air) Wall Tech Note

Don’t miss a single sound.

Designing an Air Wall System Using IR Technology

The rst consideration in designing a system is to determine whether you are designing a single channel system or a multiple channel system. For single channel systems, there are two possible design methods and for multiple channel

systems, only one of those methods is possible.

Method 1: Single Channel Air Wall System Using Auto-Seek (No RF Switcher)

This method uses Listen’s Stationary IR product type. The auto-seek function of the LR-42/44 receivers is used to

automatically search for a transmission channel in the room or area of a room where radiators are active. Four transmission channels are used. When a receiver is in auto-seek, it seeks for an active transmission channel on channels 1, 2, 3 and 4 and then stops on an active channel. When it loses the IR signal, it seeks for another signal on any one of the four channels.

Key Concept: It is important to understand that interference will occur if two different transmitter/radiator

combinations are set to the same channel.

Radiators are placed in each room on transmission channels shown in diagram 2. When the air walls are closed all

radiators are active and the auto-seek function of the receivers is used to nd the channel in any given room. For example, let’s say that one room is on channel 3 and another room is on channel 2. When a user steps into the

rst room, the receiver will nd this channel and lock on to it. When the user goes to the next room, the receiver

will unlock from channel 3 and lock on channel 2.

Once air walls are opened, the interior room radiators are turned off by not routing any audio to the

corresponding transmitters. When this happens the radiators are deactivated after 30 minutes. The exterior room radiators are designed to radiate enough IR to cover the interior room space.

Summary

Radiators are placed in each room.

Radiators in exterior rooms are designed such that when the interior walls are open, they radiate sufcient IR into

interior rooms.

When the air walls are open, the interior radiators must be turned off to prevent interference caused by two

different transmission systems on the same channel. Radiators can be turned off (after 30 minutes) by not routing any audio to the corresponding transmitter.

Receivers are set to auto-seek. In this function, the receivers search for a transmission channel and then locks on

to that channel. When the transmission is lost, the receiver unlocks and looks for another transmission channel.

Let’s use an example to design a system for the ABC Convention Center. See diagram 2 and 3 for this discussion.

Refer to the diagram 2 that shows the air walls CLOSED. Rooms A and G are on channel 1, rooms B and H are on channel 2, so on and so forth. Each room has one to two radiators to cover the space. Rooms A, D, E and H have two radiators that are pointed to the interior space so that when the air walls are opened, they radiate enough IR to cover the interior rooms.

Now refer to diagram 3 showing the air walls OPEN. Notice that the radiators in rooms B, C, F and G are tuned off (**because no audio is being routed to their corresponding transmitter) and the radiators in rooms A, D, E and H ll the

interior rooms.

Page 2

Listen Technologies Corporation • 14912 Heritagecrest Way • Bluffdale • Utah 84065-4818 U.S.A.

+1.801.233.8992 • +1.800.330.0891

North America • +1.

801.233.8995

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Listen IR Divisible (Air) Wall Tech Note

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Ch. 1

Ch. 4 Ch. 4

A E

Ch. 3 Ch. 3

B F

Ch. 2Ch. 4

C G

D H

Ch. 3 Ch. 3 Ch. 2 Ch. 2

Diagram 2. Single channel air wall system using auto-seek, 8 room air wall system with all air walls CLOSED.

Ch. 1 Ch. 1

Ch. 4 Ch. 4

A E

** **

X X

B F

C G

D H

Ch. 3 Ch. 3 Ch. 2 Ch. 2

Diagram 3. Single channel air wall system using auto-seek, 8 room air wall system with all air walls OPEN.

** These radiators are deactivated. This accomplished by not routing audio to the corresponding transmitter.

After 30 minutes, the radiators will be turned off.

Listen Technologies Corporation • 14912 Heritagecrest Way • Bluffdale • Utah 84065-4818 U.S.A.

+1.801.233.8992 • +1.800.330.0891

North America • +1.

801.233.8995

fax

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Listen IR Divisible (Air) Wall Tech Note

Don’t miss a single sound.

Method 2: Single Channel Air Wall System Using RF Switcher/Distribution Amplier

There are four main blocks to designing such a system (see diagram 4):

IR transmitter (modulator) IR radiator (emitter)

Audio Matrix Mixer RF Switcher/Distribution Amplier (it is possible for the audio matrix mixer and RF Switcher/Distribution

Amplier be the same device)

For each of these blocks, here are the specic products that Listen recommends you use:

IR transmitter (modulator)

• Listen LT-82 IR radiator (emitter)

• Listen LA-140

Audio Matrix Mixer

• No recommendation

RF Switcher/Distribution Amplier

• Extron MAV Plus or similar

Diagram 4 shows how to implement the ABC Convention Center for ONE channel. In this case, you would specify a Listen

LT-82 for the transmitter and an LA-140 for the radiators. Multiple channels for language interpretation are shown later in

this document.

Microphone mixer

output from each

room

Audio

Matrix

Mixer

Audio output from

matrix mixer

IR Transmitter

RF Output (2-8 MHz)

from IR Transmitter

(LT-82)

RF Output to each

room radiator zone

Switcher/

Distribution

Amplier

Radiators (emitters)

Page 4

Control System

IR Transmitter

(LT-82)

Control System

Radiators (emitters)

Diagram 4. Single channel air wall system using RF switcher/distribution amplier

Listen Technologies Corporation • 14912 Heritagecrest Way • Bluffdale • Utah 84065-4818 U.S.A.

+1.801.233.8992 • +1.800.330.0891

North America • +1.

801.233.8995

fax

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