RCA H5450 ユーザーズマニュアル

Single short beep 

Successful key entry 

Single long beep 

Successful operation

triple short beep 

Power oN (cordless handset)

 

Unsuccessful key entry

a long warbling tone (cordless handset)  Signals an incoming call 

one long beep 

confirmation tone

one long beep and two short  

beeps every minute 

low battery warning