AASTRA DT292 for BusinessPhone User Guide EN - Manual (Page 106)

Reference
DT292 106
Phone signals
The Cordless phone signal certain events audibly and visually as
described below.
The Cordless phone also generates audible ring signals, alarm
signals and warning tones, and key clicks.
Signal Meaning
Red warning light Incoming call
Message waiting
Battery almost empty
Cordless phone out of range or not connected
Sound Meaning
Ring signal Incoming call
Alarm signal 4 short beeps every 30 seconds: battery almost
empty
4 short beeps every 2 minutes: Cordless phone
out of range or not connected
Key click You hear this each time you press a key (when
selected).
Warning tone You have pressed a key which has no function.