Millbank Talisman Installation Manual

TALISMAN

DYNAMIC LOOP AMPLIFIER SYSTEMS

_______________________________

INSTALLATION GUIDE

Publication Code TAL-DLS-3_TIG Issue 3

TAL/DLS1/3 TAL/DLS5/3

Part No. 7157106 Part No. 7157206

PLEASE NOTE: THIS MANUAL AND THE NOTES CONTAINED HEREIN, IS COPYRIGHT AND MAY NOT BE

REPRODUCED EITHER WHOLLY OR IN PART, IN ANY WAY WHATSOEVER, WITHOUT WRITTEN CONSENT

OF FEDERAL SIGNAL LIMITED.

PUBLICATION OF THIS INFORMATION DOES NOT IMPLY ANY AUTHORITY OR LICENCE FOR THE

UTILISATION IN ANY MANNER, IN ANY COUNTRY, OR ANY PATENTED OR REGISTERED DESIGN

FEATURES, MECHANICAL, ELECTRICAL OR AESTHETIC.

MILLBANK ELECTRONICS

is part of:

FEDERAL SIGNAL LTD

Signal House, Charter Way, Hurdsfield Industrial Estate, Macclesfield, Cheshire, SK10 2NF, England

TEL: [phone] FAX: [phone] e-mail: [e-mail]

Talisman III Dynamic Loop Amplifier Systems (TAL/DLS1/3 & TAL/DLS5/3)

Publication Code TAL-DLS-3_TIG Issue 3 Page 2

Designed by Millbank Electronics

Manufactured in the UK by Federal Signal Limited

Federal Signal Limited operate a Quality Management

System which meets the requirements of

BS EN ISO 9001 : 1994

Federal Signal Limited is registered by the Lloyds Register

Lloyds Register certificate of Registration No. 923077

Product Compliance to EC directives for Standard Products

All standard products conform to the relevant directives,

regulations and standards for electronic and associated apparatus.

The equipment is CE marked both on the apparatus and the packaging.

The Modular range of products for use in Mainframes must be used

in the configuration as described in the product literature.

Failure to use the modular products in the manner described

will invalidate the EC Compliance.

Our products meet the appropriate British and International standards. A product “Declaration of Conformity” Statement is

available for each of the product ranges (available on request). This covers both the EMC and Low Voltage Directives.

UNPACKING

While all Millbank equipment is carefully packed to prevent damage in transit, we recommend that

the equipment is unpacked and inspected immediately on receipt. If damage has

occurred please advise your carrier and your supplier who will arrange appropriate action.

If it is necessary to re-pack the equipment for onward shipping or returning to Millbank for service

PLEASE ENSURE THAT THE ORIGINAL PACKING OR EQUIVALENT IS USED.

For further technical information please contact

our Customer Services Department.

on + 44(0) 1625 666600

or E-mail: [e-mail]

KEEP THIS INFORMATION IN A SAFE PLACE

Equipment Serial No ........................................................................................................................

Supplied by ........................................................................................................................

........................................................................................................................

Date ........................................................................................................................

Talisman III Dynamic Loop Amplifier Systems (TAL/DLS1/3 & TAL/DLS5/3)

Publication Code TAL-DLS-3_TIG Issue 3 Page 3

1. INSTALLATION

1.1 Precautions
IMPORTANT: Before operating the PAC Amplifier please take note of the following points:

1.1.1 Ensure that the equipment is connected to a suitable mains supply. The equipment is supplied configured
for 230V 50/60Hz AC operation.

1.1.2 For mains connections other than the UK, refer to the local requirements for connections to supply.

1.1.3 Always ensure that the equipment is properly earthed (grounded). Operating without an earth is dangerous
and may cause high levels of audible hum from the loudspeaker outputs.

1.1.4 Avoid siting the equipment in locations exposed to direct sunlight, near heaters or other heat sources. Avoid
locations with high humidity or dust levels. Do not obstruct the ventilation slots in the amplifier case and, if
the amplifier is rack-mounted, ensure that a 1U ventilation panel is fitted above the unit.

1.1.5 Never remove the top cover of the amplifier with the AC mains supply connected. All internal servicing
should be performed by a competent / qualified engineer.

1.1.6 Never make an internal adjustment when the AC supply is connected.

Fuse Holder

IEC Mains Inlet Socket

13A Mains Plug Wiring (UK only)

Green/Yellow

Earth

Blue

Neutral

Brown

Live

Fuse

5A Max.

Talisman III Dynamic Loop Amplifier Systems (TAL/DLS1/3 & TAL/DLS5/3)

Publication Code TAL-DLS-3_TIG Issue 3 Page 4

2. WHY INDUCTION LOOPS ?

2.1 Introduction

The problems faced by the hearing-impaired are rarely appreciated by those with normal hearing.
Unfortunately hearing aids give only partial restoration of hearing with the added disadvantage that the built­in microphone cannot mimic the normal ear/brain ability to differentiate between distant, wanted sounds and
nearby, unwanted noises, and so to distinguish speech clearly from a combination of direct, reflected and
reverberant sounds. For instance a hearing aid user attending a concert or play may turn up the volume
control in an attempt to improve intelligibility, invariably resulting in an increase in interference from nearby
coughs, rustles, etc., sometimes to painful levels.

All these problems can be overcome by feeding microphone signals or the existing public address (PA)
system audio directly to the hearing-aid so that only the wanted sound (without auditorium reverberation,
audience noises, etc.) is reproduced.

This can be achieved by driving audio frequency currents around a large loop of wire to generate a magnetic
field (varying in sympathy with the PA program material) and which could be picked up by suitable
equipment. Specially designed headsets are available from a number of manufacturers such as Beyer,
Danavox and telex which have applications in high-noise environments for paging/life-safety and for silent
reproduction of commentary in museums and art galleries.

However, since 1974 all UK National Health Service hearing aids have had a switch to select M (internal
microphone) or T (telecoil pick-up), the T position being originally intended for use with telephone handsets
(later designs of telephone have proved unsuitable for this use). ‘AFILS’ (Audio Frequency Induction Loop
System) are designed to work efficiently, taking into account the positions and electromagnetic
characteristics of the internal pick-up coils normally fitted to hearing aids.

Now with a suitably installed AFILS the hearing impaired can appreciate and enjoy everything that those with
normal hearing do and, as mentioned above, the same type of system can be used to provide paging/life
safety communication in very noisy areas, secret paging for security staff, disturbance free audio for spoken
commentary systems or individual AFILS for booking offices, bank tellers etc.

2.1 The MILLBANK Dynamic Loop System

The dual purpose design allows for assisted listening of the hearing impaired and for applications such as
commentary systems in museums and art galleries.

The audio requirements for the two applications are different; a hearing impaired user requires tight control
of dynamic range and restricted bandwidth to enhance intelligibility by maximising perceived volume while
limiting maximum signal peaks and frequencies. A non hearing impaired user, however, may require less
dynamic range compression and a wider bandwidth.

The Talisman range of audio induction loop amplifiers is unique in that it provides switch selectable options
to cater for these alternative uses. The bandwidth may be set to either 5KHz or 10KHz high frequency roll off
and the dynamic range compression circuit is switchable either on a peak limiter (to prevent distortion in
wide dynamic range applications) or as a dual time constant compressor reducing the dynamic range to no
more than 9dB peak to average for assisted listening applications.

A combined voltage and current feedback technique is used to optimise drive into a wide range of loop
impedances. This system overcomes the disadvantages normally associated with amplifiers using voltage
feedback only. Radio frequency interference (R.F.I.) is prevented by amplitude limiting and low pass filtering
the signal prior to the driver stage. Unlike current feedback only designs, the TAL DLS output stage cannot
clip when driving inductive loads as voltage feedback takes over when the clipping threshold is approached.
Importantly, the feedback configuration means that the dynamic loop system is stable into highly inductive,
multi-turn loops.