rately. The microphone additionally transmits the ambient
noise and words spoken in the room. This is useful if the
receiver does not have an individual microphone or if the
hearing aid does not allow to use its microphone and the
telephone coil together (mode “MT”). Via a control input a
signal sound can be triggered. A connection cable with a
standard SCART plug for TV sets and a cable of 35 m
length for setting up the induction loop are supplied to-
gether with the unit.
3.1 Operational principle
A cable is laid as an induction loop into the floor, the wall, or
into the ceiling. Within this loop, according to the audio
source, a magnetic field is created which is received with
the “telephone coil” of the hearing aid or another inductive
receiver and is reconverted into sound. It is possible to oper-
ate within an induction loop as many receivers as desired.
4
Installation and Setting into Operation
4.1 Setting up the amplifier
Prior to setting up the amplifier glue the four self-adhesive
rubber feet under the unit (as shown in figs. 1 and 2). For
operation with a microphone, the amplifier should be set up
outside the loop because of the increased susceptibility to
acoustic feedback.
4.2 Induction loop
The LA-400 allows to realize an inductive sound reproduc-
tion system for an area of up to 40 m
2
. As a loop, the sup-
plied cable is laid with a single winding at the edge of the
hearing area. The distance to ear level or to the receiver
should be approx. 1 to 2 m. It should be avoided to lay the
loop at different heights.
Magnetic fields (e. g. caused by transformers, high
power cables, or fluorescent lamps) and metal parts in
floors, ceilings, and walls may impair the operation of the
induction loop. Therefore, prior to laying the cable defini-
tively, make a trial run to determine the optimum loop posi-
tion. When laying the induction loop in tubes, these must be
made of plastic as metal tubes will affect the magnetic field
of the loop.
Shorten the loop cable if it is not required in its full length,
however, not shorter than 19 m, otherwise this value would
CAUTION
All connections should only be made by qualified person-
nel and in any case with the amplifier switched off.
12
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