When using a headset, the phone can provide additional audio alerts through that headset, These alerts are in addition to the phone's normal visual alerting and ringer.
The phone can provide headset alerts when it goes off and on hook. It can also provide a headset alert when calls are waiting to be answered. That includes calls waiting to be answered when you already have a call connected.
Disabled – The phone does not provide any additional alert sounds through the headset.
Switch hook only – The phone provides alerts sounds when the phone goes off-hook (a single click) or back on-hook (a double click).
Switch hook and alert – The phone provides alerts as above plus an additional alert (three clicks) whenever a call is waiting to be answered.