Sony Ericsson Cordless DT590 - Manual (Page 148)

Reference
MD Evolution – Cordless DT590 148
Phone signals
The Cordless phone signals certain events audibly and visually as
described below.
The Cordless 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.
Cordless 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: 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.