ET120 & ET60 Installation & Maintenance Manual
Introduction
Induction Loops (AFILS) use a feature provided by all hearing aids (both analogue and digital types)
which carry NHS or similar approval or comply with IEC118-1, to deliver high quality sound directly to
the hearing aid. The main advantages of AFILS (Loop systems) over other forms of assistive listening
devices are the fact that the hearing aid user always carries and maintains their own receiver and the
fact that the system is totally discreet.
Suitability
The ET 60 and ET120 are wall mount AFILS amplifiers and are suitable for use in rooms, which require
induction loop coverage, such as meeting rooms and reception areas. The ET60 and ET120 are
designed to be connected to the mains through a fused spur, and are designed for “24/7” operation.
The ET60 and ET120 are not designed for areas, which need secure or low spill type loop installations,
for this we suggest the SecureT amplifier, which is housed in the same type enclosure and provides two
drive outputs for low spill pattern loops.
System Design
A basic loop system is quite simple to put together. In fact it is rather like a standard sound system but
with the loudspeaker replaced by the induction loop.
Sometimes a public address or sound system may already be installed, or perhaps a more sophisticated
arrangement may be planned with inputs from various sources.
Where a satisfactory sound system is already installed the loop amplifier can be fed from the mixer or
pre-amplifier stage of the system. This will save on duplication of microphones if these have been well
chosen and sited in the first place but still give independent control of signal from the loop.
In the absence of an existing sound system it will be necessary to provide microphones and inputs to
the loop amplifier for any other signals. When microphones are to be used it is vital that they are
positioned to pick up sound, which is free from reverberation and other noises. If the microphones
receive a poor signal then the signal transmitted to the listener will be poor no matter how good the
design of the loop and other equipment. It is also necessary to ensure that the microphones are
matched electrically to the amplifier so that it is 'driven' adequately when the loop is in operation.
When positioning microphones in rooms, the microphones should be as close to the person speaking as
is practicable, for example in a classroom if the microphone is placed in the ceiling in the room centre,
the loop microphone will be further away from the speaker than the microphone in the hearing aid of
someone sitting on the front row of the class!
Product Overview
The wall mount amplifiers have been designed to be as flexible as possible, and carry a wide range of
inputs, there are connections for two types of microphone and two types of line input. Please note only
one microphone and one line input may be operated at a time.
The amplifier contains a high quality compressor limiter with a large dynamic range, and metal loss
correction to restore the high frequencies in buildings with large metal contents.
Operation
The Easy T loop amplifiers are fully automatic in operation; once commissioned the unit should not be
adjusted by the user.
Maintenance.
It is a recommendation of BS7594 that a maintenance procedure is in place for Induction Loop systems,
our recommended maintenance schedule should be as follows.
Monthly:
Using a loop receiver (such as the ETRX) listen to the area covered and check the
audio is being heard and is not distorted.
Quarterly:
Check all inputs are working individually to the loop, and test quality using the loop
receiver.
Yearly:
Engineer Call to check system inputs and loop field strength with a calibrated field
strength meter, such as the ETFSM.
Document DCC ET12 7001-03 Rev 1 Aug 2005
Page 2 of 8
