AASTRA DT590 for MD Evolution User Guide EN - Manual (Page 148)

Reference
MD Evolution – Cordless DT590 148
Phone signals
The phone signals certain events audibly and visually as described
below.
The phone also generates audible ringing signals, alarm signals
and warning tones, and key clicks.
Signal Meaning
Red warning light Incoming call.
Message waiting.
Battery almost empty.
Phone out of range or not connected.
Sound Meaning
Ringing signal Incoming call.
Alarm signal 4 short beeps every 30 seconds: battery almost
empty.
4 short beeps every 2 minutes: 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.