Signal tone	Red LED	Function / Meaning
No tone	Flashes every 344 sec.	Normal operating state, automatic self-test
Loud interval tone at intervals of 0.5 sec.	Flashes every 0.5 sec.	Alarm state
Short signal tone every 40 sec.	off	Battery change indicator, please renew detector
3 short signal tones every 40 sec.	off	Fault / contamination, please renew detector
No tone	Flashes every 10 sec.	Alarm mute
Loud interval tone	Flashes every 0.5 sec. as long as the detector head is pressed	Function test