Network
1) A series of controllers, all connected via a communications cable.
2) A group of computers, all connected via a communications cable.

Normally-Closed
The state of an input device that continually keeps a circuit closed or complete until forced by an action or event to open that circuit. See Input.

Normally-Open
The state of an input device that continually keeps a circuit open or incomplete until forced by an action or event to close that circuit. See Input.