Direct contact. This type of contact allows the power to flow from the left rail to the right rail when the value is 1.

Inverted contact.This type of contact allows the power to flow from the left rail to the right rail when the value is 0.

Positive sensing contact.This type of contact acts as a pulse. When there is power from the left rail, the contact value momentarily switches to 1. When there is no power, the contact value is 0.

A negative sensing contact acts as a pulse. It has the reverse effect of the Positive sensing contact. When there is power, the contact value is 0. When there is no power, the contact value momentarily switches to 1.

A direct coil writes a value to a database item. If there is power from the left rail, it writes a 1 value. If there is no power from the left rail, it writes a 0 value.

Inverted coil. This output writes a value to a database item. It has the reverse effect of a direct coil. If there is power from the left rail, it writes a 0 value. If there is no power from the left rail, it writes a 1 value.

Set coil. This output is set to 1 when there is power from the left rail. Set Coil works in a similar way to an 'On' switch—when it is set to On by the power from the left rail, it remains On until it is specifically set to Off (by a reset).

Reset coil. This output is set to 0 when there is power from the left rail. Set Coil works in a similar way to an 'Off' switch—when it is set to Off by the power from the left rail, it remains Off until it is specifically set to On (by a Set).

Positive sensing coil. This output acts as a pulse. When the input from the left rail changes from 0 to 1, the coil outputs a 1 value. When the next rung of the Ladder Diagram is executed, the positive sensing coil reverts to having a 0 output.

Negative sensing coil. This output acts as a pulse. When the input from the left rail changes from 1 to 0, the coil outputs a 1 value. When the next rung of the Ladder Diagram is executed, the positive sensing coil reverts to having a 0 output.