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Praesideo public address system from Bosch

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Bosch ’s new Praesideo satisfies the often stringent demands placed on voice alarm systems in virtually all types of building. Praesideo is also a fully functioning public address system.

There are currently a number of clearly evident trends, which influence the choice of evacuation/ emergency systems. The first is a growing public indifference to alarm signals. Time and time again, it has been seen that standard alarm signals and tones simply do not convey enough urgency to mobilize the public into prompt action (as a parallel: how many people react on hearing a car alarm?) There is a definite advantage in using voice alarm systems, which are much more effective in drawing attention to potential danger and communicating instructions in the event of an emergency. A combination of spoken message with alarm tone works particularly well.

This trend is mirrored in the increasingly strict requirements for evacuation systems in new (larger) buildings. Simple alarm installations often do not meet these requirements, which require a more comprehensive voice alarm system for the protection of people who will work at, live in, or visit the premises. Fire Brigade approval of such installations is now virtually mandatory.

Increase in installers’ liability

Then there is the matter of liability. In the past, meeting the requirements laid down in a tender was often subject to interpretation by installers or building contractors. But today’s requirements are stricter and more clearly defined. What’s more, if an incident should occur (e.g. a fire) whereby property is damaged or people injured due to inadequate installation or functional limitations of the emergency sound system, it is the installer who may be held at least partly responsible, and not the company who manufactured the evacuation system. There is no point in taking risks. The safest bet is to specify a system, which conforms to all the relevant norms. The Praesideo digital public address and emergency sound system from Philips addresses all of these issues. Key features to help achieve this include:


The Praesideo fully meets the requirements of many of the world’s main

standards on emergency sound systems (also known as voice evacuation or voice alarm). For instance, it is fully compliant with IEC 60849, which is the International standard applying to sound systems for emergency purposes to be used to effect a rapid and orderly mobilization of occupants in an indoor or outdoor area in an emergency situation.


The Praesideo system basically consists of a network controller, call stations and control panels, and multi-channel power amplifiers. Unlike traditional PA systems, the Praesideo uses a network configuration rather than having all system elements connected to a

central controller. By connecting the network ends together, a redundant loop is created so any break in the main cable loop does not affect operation. Redundancy also means that the system can function even without the central (network) controller; if necessary, a fireman's panel can take control and make all call announcements to every amplifier in the system. And automatic switching to back-up equipment or battery power supplies takes place if operation is disrupted or the main power supply fails.

Attracting attention.

Verbal alerts, pre-recorded messages and alarm signals can be broadcast throughout the entire premises, or to selected areas. The network capacity allows for as many as 28 different uncompressed audio signals to be broadcast simultaneously to single or multiple zones.

Signal integrity.

Digital audio ensures a high degree of signal integrity, and the use of fibre optic cables to distribute all data eliminates interference from sources such as lift motors and high-frequency fluorescent lighting. Ground loops that may cause hum or crosstalk between the audio channels are a thing of the past. This means messages are clear and easy to understand. A single network cable transmits all audio and control data; no extra wiring is necessary.


Automatic and continuous system monitoring is carried out from the microphone capsule of a call station all the way to the far end of the loudspeaker cable.

World’s fully digital pa/emergency system

The Praesideo is the world’s first fully digital PA/emergency system. By keeping all audio processing, communication and control functions entirely in the digital domain, the Praesideo is able to offer significantly better audio performance, as well as increased functionality. Signals of CD quality make sure that messages are just as clear coming out of the system as they are when they go in. And a vast amount of customised messages of all length can be recorded and stored on the compact flash card built in the network controller, the only limitation is the chosen memory capacity. Up to four different messages can be played simultaneously to different zones. Furthermore, the quality of digitally stored messages is guaranteed by continuous monitoring of the content. Digital also means programming power and scalability. Messages can be selected for broadcast from any call station or contact input. The system is fully programmable, which brings flexibility in terms of zone assignments and numbers, call stations, audio inputs and outputs, control inputs and control outputs.

Simplified installation through distributed functionality

Whereas many competitive systems offer an exhaustive list of part numbers to choose from, the Praesideo was deliberately created with a minimum of elements to simplify ordering and installation. The key to this simple system philosophy is distributed functionality. Digital signal processors (DSPs) have been built into almost every system unit, which means that, as the system is expanded, the processing power automatically expands with it. This brings true scalability in system design, and also means there is no need to add extra equipment like equalizers or delay units.

Every audio unit contains programmable multiband parametric equalisers for each individual input or output. Call stations also incorporate a limiter. Power amplifiers have additional delay lines per channel for proper loudspeaker alignment, as well as inputs for ambient sensing microphones with integral, automatic volume control (AVC). Each unit can therefore be optimised individually for the ambient acoustical environment and/or required functionality.

Additional supporting functions normally required for emergency sound systems, like audio path supervision, overload/short circuit detection and spare amplifier switching facilities are also built-in, which simplifies installation even more. Loudspeaker line supervision is based on communication over the loudspeaker line itself, between the power amplifier and a small transceiver unit at the end of the line. This does not require additional wiring, nor does it interfere with audio signals present on the same line.

Each Praesideo system element also has its own supervised control inputs and control outputs. As a result, new connections can be made locally, without having to run cabling back to the network controller. This obviously saves installation time and, given that the cost of cabling and associated labour can add up to more than half of the total installation costs, also represents a major financial advantage.

Freedom in locating equipment

The Praesideo’s modular architecture gives real freedom in system design. The daisy-chain network topology means system elements can be connected (and added at a later date) to virtually any point. Smaller systems can easily be expanded to match changing requirements, for instance by creating new zones. And the flexible system architecture allows any type of equipment to be located wherever is suitable in the building (e.g. power amplifiers closer to loudspeakers). The non-redundant daisy-chain topology can be made redundant by creating a loop using only one additional cable. These topologies may be extended using network splitters to create (non-redundant) branches.

Easy interfacing with external equipment

By accommodating the TCP/IP protocol, via Ethernet on the network controller as well as a standard RS232 interface, the Praesideo interconnects easily with many other brands and types of third-party systems and peripherals: from simple contact inputs/outputs right up to Internet. Systems for fire alarm, remote control, automatic announcements, plus passenger information displays can all be interfaced. This means the Praesideo can be configured to automatically broadcast alert announcements and evacuation announcements to different zone groups on receiving location-dependent inputs from a fire alarm system. A database with different standardised alarm and attention tones is available, and the number of simultaneously broadcast tones is only limited by the number of available audio channels (28).

Simple (remote) configuration and diagnostics

The Praesideo uses web-based technology to enable authorised users to access and monitor the system from any location. Remote diagnostics and logging are also possible. The network controller has an integrated web server, so system (re-)configuration is carried out quickly and easily from a PC running a standard Internet browser and logged in to the network. This software- based configuration of all functional parameters means no programming is required at the equipment end, and also eliminates time-consuming changes in the system. The result: drastically reduced installation and commissioning time.

For instance, the software allows configuration of:

  • Routing of all zones and audio inputs
  • Audio levels and functions (e.g. parametric equalization)
  • Priority levels (up to 256)
  • Descriptions of all devices
  • Sequences and timing of messages & music
  • Definitions and functions of call station keys and control input contacts
  • Downloaded WAV-files for pre-recorded messages

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