A value of 1 (=Sounder fault) this means there was no sound detected in 5 seconds of the sounder being switched on. A value of 2 (=VAD fault) means there is no current being drawn by the LED’s. A value of 3 (=Sounder and VAD fault) where neither of the above elements are operating correctly.; EN54-23 approved Flash rate of 0.5Hz Synchronisation of 'alert' and 'evacuate' tones Synchronisation of visual indicator flash Individual and group addressing Unique acoustic and VAD self-test Built in isolator