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IOM-INT | V1.1 | 2010.12 Installation and Operation manual Bosch Security Systems B.V.

4.2 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.

4.2.1 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 4.3). 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 4.3 Directional characteristics of the receivers

4.2.2 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 4512/00 radiator is twice as large as the

coverage area of the LBB 4511/00. 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 4.4 and Figure 4.5. The

radiation pattern is the area within which the radiation intensity is at least the minimum

required signal strength.

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Bosch INTEGRUS Service Manual Page 18