An actuator is a transducer that accepts a signal and converts it to a physical action. In other words, an actuator causes an action to occur relating to the data that was sent to it by via an NCAP. Data written to an actuator is held in an input register until the trigger is received.
An actuator can also describe itself to the network, making it easier for automatic system configuration. It does this by the use of TEDS. The TEDS can be uploaded to the system upon power up or request. It also serves as documentation.