System Technology; Ir Radiation; Signal Processing - Bosch INTEGRUS Installation And Operating Manual
Digital infra-red language distribution system
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INTEGRUS | Digital Infra-red Language Distribution System
1.2 System technology
1.2.1
IR radiation
The Integrus system is based on transmission by modulated infra-red radiation. Infra-red radiation forms part of the electro-
magnetic spectrum, which is composed of visible light, radio waves and other types of radiation. It has a wavelength just above
that of visible light. Like visible light, it is reflected from hard surfaces, yet passes through translucent materials such as glass.
The infra-red radiation spectrum in relation to other relevant spectra is shown in Figure 1.2.
%
100
75
1
50
25
4
2
0
400
500
Figure 1.2 Infra-red radiation spectrum in relation to other spectra
1.2.2
Signal Processing
The Integrus system uses high frequency carrier signals (typically 2-8 MHz) to prevent interference problems with modern light
sources (see section 1.3.2). The digital audio processing guarantees an constant high audio quality.
The signal processing in the transmitter consists of the following main steps (see Figure 1.3):
1.
A/D conversion -Each analogue audio channel is converted to a digital signal.
2.
Compression - The digital signals are compressed to increase the amount of information that can be distributed on each
carrier. The compression factor is also related to the required audio quality.
3.
Protocol Creation - Groups of up to four digital signals are combined into a digital information stream. Extra fault
algorithm information is added. This information is used by the receivers for fault detection and correction.
4.
Modulation - A high frequency carrier signal is phase-modulated with the digital information stream.
5.
Radiation – Up to 8 modulated carrier signals are combined and sent to the IR radiators, which convert the carrier signals
to modulated infra-red light.
In the IR receivers a reverse processing is used to convert the modulated infra-red light to separate analogue audio channels.
Audio
A/D Conversion
Channel
& Compression
4x
4x
Audio
A/D Conversion
Channel
& Compression
Figure 1.3 Overview of the signal processing (for one carrier)
5
600
700
800
3
900
1000 nm
Protocol Creation
Carrier (to IR Radiators)
& Modulation
BOSCH Security Systems | February 2003
1
Daylight spectrum
2
Sensitivity of the human eye
3
IR radiator
4
Sensitivity of IR sensor
5
Sensitivity of IR sensor with
daylight filter
en |
7
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