LCD Display Soft Key Definitions
Soft Key Definition
ABR Activates Automatic Busy Redial after dialing a busy outside telephone number
ACB Activates Automatic Callback after reaching a busy station , CO line, or CO line group
BUSY (Busy Override) Sends a call-waiting tone to a busy station
CONF Initiates or completes a conference
EXEC (Executive Override) Breaks into the conversation of a busy called station
EXIT Exits you from a conference; remaining parties are connected
JOIN Joins all parties to a conference while on a conference call
LINE Adds a CO line to an existing call while in the Conference mode. The LCD prompts you to access a CO line after you press this key
MESG Sets a message waiting indication at a busy or unanswered station
OVRD Overrides options, busy mode, or overrides Do Not Disturb mode
PGE Enables you to enter a Page Group number (01-16)
RING Makes a called station ring when making a voice announce call to the station
RLS Disconnects a call and returns telephone to the idle state
RTRN Terminates a feature operation and to return to a previously displayed state
SPLT Enables you to break off from a conference call with another conference call member for a private conversation (split). You can use the Join key to reconnect both of you back into the conference. 
STA. Adds a station to an existing call while in the conference mode.  The LCD prompts you to dial a station number after you press this key
TALK Makes a voice announcement to a called station that is ringing
TRNS Initiates or completes a Transfer while on an outside call.  Press once for an immediate or announced transfer, depending on system programming.  Pressing TRNS again completes the transfer.