---| |--- (Normally Open Contact) is closed when the bit value stored at the specified is equal to "1". When the contact is closed, ladder rail power flows across the contact and the result of logic operation (RLO) = "1".
Otherwise, if the signal state at the specified is "0", the contact is open. When the contact is open, power does not flow across the contact and the result of logic operation (RLO) = "0".
When used in series, ---| |--- is linked to the RLO bit by AND logic. When used in parallel, it is linked to the RLO by OR logic.