Abstract: In conjunction with a conventional power operated overhead door, such as a garage door, which has wire cables attached to the door for assisting in raising (opening) and lowering (closing) the door, a cam plate or dog having a toothed edge can be pivotably moved to instantaneously clamp or bind against the wire cable to stop its downward movement in the event any obstacle, such as a small child, is detected in the path of the door while it is being closed. The cam plate is biased to permit the wire cable to move in a direction to open the door.