Know-how

More than an Alarm System
 

With 200,000 m2 of exhibition space, Messe Düsseldorf is one of the largest fairground sites in Germany. The officials regard the visitors' safety as a top priority. The local NEXUS network for emergency-paging and sound-reinforcement applications, which is controlled by a C.A.S. 200 system and has been in operation since September 1999, sets new safety standards.

» An emergency-paging system must work under any conditions – otherwise, lives are at risk. Imagine what happens if an evacuation notice cannot be understood,« says Andreas Noch, head of the audio/video department at Messe Düsseldorf. Therefore, his top priority for a new emergency-paging system was that it had to be absolutely fail-safe. With this in mind, the installation at Messe Düsseldorf saw the introduction of a novelty: continuous monitoring of all system components. The core of the system – the audio-signal distribution – is based on NEXUS; this is another evidence for the system's flexibility and reliability!

The Concept

A total of 17 networked NEXUS routers were installed in various locations around the park to ensure efficient emergency paging/public address in all of the 15 exhibition halls. Because this kind of installation requires features that are quite different to what one may come across in a NEXUS broadcasting or studio environment, the contractor SAAVS Friedrich Salzbrenner GmbH developed a special C.A.S. 200 controller for this particular application of a NEXUS-driven network. In this setup, NEXUS acts as an audio router for announcements via the installed 100V-line public-address system while being controlled and monitored by the C.A.S. 200.

Transparent Networking

Each hall and the main building have their own NEXUS router feeding the power amplifiers. Thanks to this decentralized setup, each hall can function independently in emergencies – a requirement imposed by the local fire brigade. To comply with this prerequisite, every hall must allow for paging and emergency announcements even if the connection to the central monitoring station at the main building is broken.

The digital architecture of NEXUS provides several advantages for paging and public-address systems. One of them is the significantly lower wiring overhead because a single optical cable can transfer up to 128 audio channels plus control signals. Another benefit of the system is that all NEXUS units can be connected to one another using a single optical cable. This brings the estimated 100,000 meters of copper wire for the transfer of individual signals down to a mere 6,500 meters of optical cables, saving 650,000 Euro.

Reliability

The C.A.S. 200 controller of the system continuously runs test routines on the entire network. In this way, possible failures can be pinpointed and located with utmost precision. One of the main monitoring routines that were implemented at Messe Düsseldorf's explicit request is the continuous and reliable monitoring of all of the 142 speaker lines. The routine identifies cable failure, accidental grounding, and shorts even while the system is in operation. The statuses of the optical-cable network, automatic system checks, and power-amp monitoring are available at any time. Any malfunctions are not only indicated but also bypassed wherever possible: if a component fails, the system will automatically enable a preset emergency routine. For example, if a power amplifier fails, the signal is immediately diverted to a second – redundant – power amplifier. A higher degree of safety is hard to imagine.

Flexibility

Compared with Messe Düsseldorf's previous analog system, the NEXUS network sets new standards in flexibility. Just one example: Düsseldorf hosts the annual BOOT fair (international consumer show for boats and water sports). Before the opening of the fair, the engineer will identify all required emergency-paging channels and announcement counters and will enter them into the C.A.S. 200 where the settings will be stored as a status. Such a status needs to be configured only once and can afterwards be loaded every time Düsseldorf plays host to the BOOT fair. The memory system allows Andreas Noch and his team to set up the paging circuits required for all of the 55 fairs held in Düsseldorf every year, and to recall the settings by the press of a button when the time of an event comes. For additional convenience, it is possible to make the system ensure perfect automatic line routing by entering the events into a system agenda.

Even Better than the CD

In professional recording circles, NEXUS is known for its superior audio quality. Likewise, all public announcements at Messe Düsseldorf are clearly understandable thanks to a 24-bit resolution and a sample rate of 48 KHz. This is not just easy on the ears but also a safety feature, for emergency announcements will be perceived as such – and be understood. The basic sound quality is further enhanced by selective filtering and delaying of all signals using NEXUS' internal processing circuits.

Thanks to its audio quality, a similar C.A.S. 200 system at Neuen Messe München (New Fairgrounds in Munich) is used not only for emergency paging and public address but also as sound-reinforcement system for various events – an idea that was also implemented by Messe Düsseldorf. Therefore, an audio line runs from the C.A.S. 200 to the onsite recording studio. The first sound-reinforcement tests proved conclusive. Says Andreas Noch: »We use the system for three applications: emergency paging, announcements, and background music/musical sound bites, though it must be said that emergency announcements will remain our top priority. They can override and mute any other signal.«

It is no coincidence that one of the most advanced and reliable emergency-paging and public-address systems was built in Düsseldorf. The recent fire disaster at the airport still haunts people's memories. »The reliability aspect alone was not sufficient as we demanded more from an entirely new system such as a high degree of concurrency and a flexibly programmable system hierarchy,« says Noch. »We ended up with a solution that provides a lot more than we bargained for. After all, we can now tailor the address system to our customers' needs, thereby contributing to the success of a show.«