Redundancy, resilience and the ability to monitor the status of audio and control lines and report faults and errors to building or operations managers is increasingly important in critical building safety systems.
Incorporating this level of protection and reporting to each and every critical system adds dispr
oportionate cost to the hardware and the installation costs, but is nevertheless essential to ensuring the safety of those occupying the building.
In Broadcast and live production the cost and embarrassment of losing a transmission far outweighs the cost of incorporating backup strategy and hardware at the design stage. So their systems have incorporated the highest level of resilience and redundancy for many years. And as a result of increased statutory requirements in Germany following a fire at Dusseldorf Airport, these very systems were increasingly deployed in the infrastructure of larger multi-use public buildings such as conference, convention and exhibition centres, theatres, concert halls etc.
Especially true where these might be used for concerts, broadcast events, or where the building itself was modular and the audio system required rapid reconfiguration to accommodate the changing layout.
Although the on-paper costs of these broadcast style systems appeared more costly than conventional approaches, the flexibility provided by their routing capability and inherent resilience became a valuable and compelling argument for inclusion in these larger buildings.
Recent reductions in costs, due to technological developments, economies of scale and the increasing requirement to provide resilience and redundancy across many different systems, has now made these viable across a range of building sizes and types, where once the cost would have precluded their use in anything other than the largest venues and buildings.
Consequently greater consideration can now be given to handing responsibility for security and redundancy to a single, highly resilient, backbone system. Although this requires a higher level of planning, coordination and cooperation, the benefits are significant.
Stagetec Nexus comprises Euro frames loaded with the requisite number of input and output cards of 
whichever analogue or digital format required at each location. The system also carries serial data such as RS232, RS422, RS485, plus GPIs for sending or receiving the operation of switched contacts.
Frames are interconnected by dual-redundant fibre-optics, such that should one fail, be inadvertently unplugged or the cable damaged, the other would instantly and seamlessly take over – the change-over completely transparent with no break at all in the signals being carried. Current systems carry up to 256 channels of high quality audio over a single fibre.
The systems also incorporate rigorous monitoring strategies that deliver error or alarm messages to technical or operations managers to ensure that any hardware fault or damage or loss of any fibre is identified and quickly resolved.
Faults, errors or damage to the backbone may also be reported to the individual controllers for each and every system using the backbone; ensuring alarms are triggered, events are logged and any corrective strategies activated.
Hence the separate paging, voice-alarm/evacuation, HVAC control, security systems can transfer their audio and data connections to the ultra-resilient backbone, which carries them to the input/output frame closest to their destination, where they connect to the local hardware. The bi-directional data connections carry the control to the destination and return the monitoring and status data to their respective control systems.
But the benefits don’t end here. Adopting this approach enables considerably greater flexibility and reduced costs throughout th
e life of the building and its systems.
Adding connections between two areas is simply a case of connecting to spare ports in each area and setting a connection in the control system; or if there are no spare ports, adding a new hot-swappable card at either end to provide them. Moving a connection’s destination from one area to another only requires a change to the routing and a connection at the new output port. While adding new areas or connecting to other buildings just needs a new fibre path and a card frame at the destination, which may be many kilometres away.
Because every frame has two control ports, there are multiple points of control –and no single point of failure; each external system that needs to control or monitor signal routing can connect to the frame closest to it, while the whole system can be configured and managed from a single port – any of them.
This type of system delivers many more efficiencies than it is possible to detail here. For example it permits considerably more efficient use of the available ports on the connected systems. A single audio or data output port can connect to many different destinations; simultaneously or individually, in a sequence or under external control. The system can also include embedded control functions, triggered by internal monitoring, external switches, tallies or serial data.
Space precludes any more detailed investigation of the benefits of a resilient backbone; the first draft of this article was over twice the length! Suffice to say adopting this backbone strategy delivers significant cost benefits during installation and throughout the life of the building, and gives levels of safety, resilience and flexibility that would simply not be possible using disparate systems, each with their own control system and fixed infrastructure.
First published in the Autumn 2006 issue of ISCE Magazine
By Chris Collings
Aspen Media Ltd