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INTEGRUS | Digital Infra-red Language Distribution System en | 9

BOSCH Security Systems | February 2003

1.3 Aspects of infra-red distribution systems

A good infra-red distribution system ensures that all delegates in a conference venue receive the distributed signals without

disturbance. This is achieved by using enough radiators, placed at well planned positions, so that the conference venue is

covered with uniform IR-radiation of adequate strength.

There are several aspects that influence the uniformity and quality of the infra-red signal, which must be considered when

planning an infra-red radiation distribution system. These are discussed in the next sections.

1.3.1 Directional sensitivity of the receiver

The sensitivity of a receiver is at its best when it is aimed directly towards a radiator. The axis of maximum sensitivity is tilted

upwards at an angle of 45 degrees (see Figure 1.4). Rotating the receiver will decrease the sensitivity. For rotations of less than

+/- 45 degrees this effect is not large, but for larger rotations the sensitivity will decrease rapidly..

Figure 1.4 Directional characteristics of the receivers

1.3.2 The footprint of the radiator

The coverage area of a radiator depends on the number of transmitted carriers and the output power of the radiator. The

coverage area of the LBB 4512 radiator is twice as large as the coverage area of the LBB 4511. The coverage area can also be

doubled by mounting two radiators side by side. The total radiation energy of a radiator is distributed over the transmitted

carriers. When more carriers are used, the coverage area gets proportionally smaller. The receiver requires a strength of the IR

signal of 4 mW/m2 per carrier to work without errors (resulting in a 80 dB S/N ratio for the audio channels). The effect of the

number of carriers on the coverage area can be seen in Figure 1.5 and Figure 1.6. The radiation pattern is the area within which

the radiation intensity is at least the minimum required signal strength.

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LBB 4511/00

LBB 4512/00

Figure 1.5 Total coverage area of LBB 4511/00 and LBB 4512/00 for 1 to 8 carriers

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Bosch INTEGRUS Manual de servicio Pagina 9