Voice Alarm (VA) Systems - Taking the Voice Sounder Route
James describes how some quite complex systems have successfully integrated voice sounders within their design and how, with the approach of the new Fire-Cryer┬« Plus seven message voice sounder range, Vimpex are initiating a new phase in the use of voice sounder technology. He goes on to discuss how Vimpex’s expertise, gained over several years at the forefront of voice sounder design, is now paying dividends and enabling them to consult their customers on how to best integrate voice sounders into complex analogue addressable fire alarm systems.
All Voice Systems Are Not Equal
Fire alarm consultants and system specifiers want an easy life.
It’s too easy to stipulate a certain standard when all it means to the specifier is a BS standards number on the page. It is only when a fire system design company comes to cost a job to that requirement does the real cost of careless specifications come to light.
This is our experience when it comes to the specification of voice alarm systems. It has become too easy for specifiers to use British Standard BS 5839 Part 8 (Voice Evacuation Systems) as a catch-all standard the moment it has been decided that voice evacuation is a necessity. In fact, specifying voice sounders for use in a voice evacuation system designed under the auspices of BS 5839 Part 1 can in many instances satisfy the key features of a Part 8 system without the cost or complex design process associated with full-blown VA systems.
Much to the distain of VA system manufacturers, there are many fire systems in the field with more than a hundred voice enhanced sounders on complex systems giving fully synchronised, multi-message announcements in a clear, unambiguous manner.
Arguments against the use of voice sounders are dissolving. With multiple sounder circuit synchronisation, up to seven pre-recorded messages available and with growing ranges of voice sounders constantly being introduced, the message is clear-that voice sounders are intelligible, loud enough and can easily be integrated into both new and existing fire alarm systems.
It is important to note that piezo-driven voice sounders do not provide nearly as clear and intelligible messaging as those that use more traditional capsule-driven loudspeakers. This is because a piezo device is designed to maximise output at a pre-determined frequency and not a relatively broad frequency range as in products like the Fire-Cryer.
Voice Sounder System Design
With seven messages and many available software configurations, it is important for the installer to understand what can be done with voice sounders and how to integrate them into a standard BS 5839 Part 1 system.
The first task of any fire alarm design is to agree the evacuation strategy and whether there is any requirement for staged or phased evacuation. Then the designer must ensure agreement with his client and the end user as to the choice of messages and preceding tones to be used in the system.
The choice of messages is extensive and with seven messages available in a single sounder, a fire alarm system can be expanded to include inputs for bomb alerts, terrorist threats, coded warnings, water leakage alerts, class change announcements, system tests, ‘all clear’ announcements, machinery shut down warnings, health and safety reminders, general alert messages, and of course ‘fire’ alarm messages. The potential is huge and with the trend for fire evacuation systems to be used for general evacuation and public safety systems, the use of multi-message voice sounders is set to boom.
Multi Message Switching
Although voice sounders are basically conventional fire alarm sounders that play pre-recorded messages, the sounders need to know what message to play and when!
In order to switch from message to message, a switching interface is installed on the sounder circuit. This is interposed between the control panel (or sounder module if on an analogue system) and the rest of the sounder circuit. The bell circuit provides power for the primary or ‘life safety/fire’ message, whist an auxiliary power supply, sometimes from the panel, sometimes external, powers the switching interface and the extra auxiliary messages. Both sounder circuits and auxiliary power supply must be rated to provide current for all sounders and any strobes on the circuit. Monitoring of the sounder circuits is not affected and the panel’s recommendations on resistance should be maintained. Figure 1 shows how Fire-Cryer┬« Voice Sounders are typically interfaced to an analogue loop.
Installation of a multi-message sounder system as an interface to a conventional fire alarm system is straightforward as the switching interface is simply installed on the bell circuit. Volt-free contacts are then required to operate additional messages. Sometimes a pre-wired voice message controller will be used to ease installation and to provide the end-user with a simple message selector.