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).
OPEN only (all LiftMaster operators) or SAFETY only (LiftMaster operators with type B2 C2 L2 T T1 or TS control wiring) after vehicle passes over treadle.
The weight of the vehicle compresses an electric switch which sends an open signal to the door.
Requires a 2-wire connection to the operator but does not require power to function