196 / General System featuresModular ICS 4.0 System Coordinator Guide P0881591 Issue 01Some display buttons, such as TRANSFER and ALL, are simplyshortcuts which are not available on a one-line display.Other display buttons, such as OK and SHOW, perform essentialfunctions. For a one-line display telephone, use the followingbuttons instead of these display buttons.Substitutes for display buttonsAll displays listed in this book are shown as they appear on thetwo-line display.Prime lineYour telephone can be programmed to select an internal orexternal line or a line pool automatically whenever you lift thereceiver or press ©. This is your prime line.Private linesA private line is exclusive to a particular telephone. Calls thatare put on hold or left unanswered on a private line cannot bepicked up at any telephone except the prime telephone.Volume barThe volume bar controls the volume of the receiver, telephoneringer, handsfree speaker, and headset. Press either end of thevolume bar √ to adjust the volume.Display button Dial pad buttonOK ˙QUIT ®ADD •SHOW £CANCEL £VIEW £OVERRIDE £BKSP √