Nortel Networks 2004 - Manual (Page 143)

Terms you should know
143
System or Switch
Your office communication system.
Switchhook
A button that the handset presses down, disconnecting your call
when you replace the handset. The handset (when lifted)
releases the switchhook and you either answer an incoming call
or you receive a dial tone to make a call.
User Interface
Screen displays that interact with the end-user as a result of an
action or event.
Volume control bar
A rocker bar you press to increase or decrease the volume of the
ringer, handset, headset, speaker and the Handsfree feature.