Switch Wiring and Relay Contacts
The data sheet for wiring relays or switch contacts using digital input/output and digital I/O card.

Switches

Switches are pretty straightforward to wire. For security reason switch contacts are always drawn in the OFF position when in systems initialize. In the case of rotary switches the wiper arm will always be connected to the first contact, which will be the off position.

Relays and Contacts
Same to switches, relays are always drawn in the off are un-operated position. Contacts may be drawn in different ways as shown below; but the middle contact (labeled 2 below) is the wiper arm and will move when the relay is energized. This contact is called the changeover contact, abbreviated CO. The top contact (labeled 1) is the normally closed, NC contact (relay not energized) and contact 3 known as normally open, NO. When power is applied to the relay coil, the NO contact is then mechanically and electrically contacted to the CO contact.