The Block Schematic opposite shows a simple voice alarm system. The diagram has been simplified for clarity.

The system shown has five prioritised inputs, input 1 being the lowest priority and input 5 being the highest priority:

a radio for playing background music
a microphone for staff announcements
an input from a time control system for shift time signals
an input from a fire alarm panel
a monitored firemans microphone.

The first three inputs provide un monitored public address functionality. Input four accepts sounder circuits from a fire alarm panel which initiate digitally stored emergency messages. Input five provides a, fail safe, monitored microphone.

A modem connection allows the router to be programmed remotely and provides remote fault monitoring and diagnoisis.

The voice alarm router directs the input signals to the amplifiers depending upon its programming. The amplifiers in this instance drive the four zones:

Directors Suite
General Office
Production
Warehouse

The amplifiers and their loudspeaker cabling are monitored by use of an End Of Line (EOL) resistor. A reserve amplifier (not shown) automatically cuts in to take over from any amplifier should a failure occur.

In some instances a minimum of two amplifiers will be required for each zone. Their loudspeakers will be interleaved so if one loudspeaker circuit fails the zone is still covered by the other amplifier.

The whole system is protected against mains failure by lead acid batteries which are normally configured to run the system for 24 hours in standby and 0.5 hours in alarm.

All voice alarm systems should comply with BS5839 Part8. We use Application Solution's ground breaking equipment for all our voice alarm installations.