1.3 Aspects of infrared distribution
A good digital infrared language distribution system
ensures that all delegates in a conference venue
receive the distributed signals without disturbance.
This is achieved by using a sufficient number of well
positioned radiators, in such a way that uniform IR
signal with adequate strength can be received at any
place of the conference venue.
When planning an infrared distribution system several
aspects influencing the uniformity and quality of the
infrared signal should be considered. These are
described in the next sections.
1.3.1 Ambient lighting
HCS-5100Plus can be operated without any problem
even if fluorescent lamps (with or without electronic
ballast or dimming facility), such as TL lamps or energy
saving lamps are switched on. (see figure 1.6).
Figure 1.6 The infrared language distribution system
using 1-8 MHz eliminates disturbance from high frequency
lighting systems
For venues with large, unscreened windows, more
radiators should be added. For outdoor use, a site test
will be required to determine the required amount of
radiators. With sufficient radiators, the receivers will
work well, even in bright sunlight.
1.3.2 Objects, surfaces and reflections
Just like visible light, infrared radiation is reflected from
hard surfaces and refracted by hyaloid (glassy or
transparent appearance) objects. Both objects in the
conference venue and structure of the walls and
ceilings will influence the distribution of infrared light.
Infrared radiation is reflected from almost all hard
surfaces. Smooth, bright or shiny surfaces reflect well.
Dark or rough surfaces absorb a large part of the
infrared energy. Normally surfaces opaque to visible
light are also opaque to infrared radiation.
Shadows from walls and furniture will influence the
transmission of infrared light. This can be solved by
using a sufficient quantity of radiators.
They should be positioned in a manner to provide an
infrared field strong enough to cover the whole
conference area.
Take care not to direct radiators towards
uncovered windows, or most of this radiation will
be lost.
1.3.3 Directional sensitivity of the receiver
The sensitivity of a receiver is at its best when it is
aimed directly towards a radiator. To minimize the
disadvantage of this aspect, HCS-5100R/RA/F receiver
adopts an ingenious structural design with peculiar
270° ultra wide angle to get perfect IR capture and
sound quality at any disposition (see figure 1.7).
Figure 1.7 Directional characteristics of the receivers
1.3.4 The footprint of the radiator
The number of transmitted carriers and the output
power of the radiator determine the coverage area of a
radiator. The total radiation energy of a radiator is
distributed over transmitted carriers. The coverage
area becomes proportionally smaller if more carriers
are used. The receiver requires a strength of the IR
signal of 4 mW/m
2
per carrier to work well (resulting in
an 80 dB S/N ratio for uninterrupted audio channels).
The cross section of the 3-dimensional radiation with
the reception level of participants is the footprint (the
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