May be used in two different ways: as an OPEN only control (all LiftMaster operators) or as an OPEN/CLOSE control (only LiftMaster operators with types B2 and S2 control wiring).
In the latter case pulling the cord will open a fully closed door close a fully opened door and reverse a closing door.
Pulling the cord whlie the door is opening will either have no effect (type B2 wiring) or will stop the door (Solid State Logic Control Board).