Vertical Communications FXS, and FXT manual Has system call you when busy station becomes idle

Display Abbreviations GCA70-349

Abbreviation	Feature	Definition
CAMP		Has system call you when busy station becomes idle.
	Camp On	When chosen as a feature, stores a button that enables
		the function.
CFWD		Forwards all of your calls to a different station
	Call Forward	location. When chosen as a feature, stores a button
		that enables the function
CALLBK	I Will Call Back	Respond to a SOHVA call with a non-verbal message.
CLEAR	Clear Features	Stores a button that clears a currently active or
		engaged feature.
CLR	Clear	Cancels a call forward condition.
CONF	Conference	Establishes a conference.
DARK	Dark (contrast)	Makes LCD screen darker.
DISP	Display	Adjusts the contrast of your LCD screen.
DND		Makes your station appear busy to other stations.
	Do Not Disturb	When chosen as a feature, stores a button that enables
		the function.
DSS/BLF	Direct Station	Stores a personal intercom number at a DSS/BLF
	Select	button.
EXIT	Exit Selection	Ends a current programming session.
EXT	System Speed Dial	Selects system speed dial numbers to access through
	By Name	the dial by name interface. (2 Line LCD)
FEAT	Feature	Presents several different features you can store at
		programmable buttons for later use.

94 Large Screen Display Speakerphone Station User’s Guide