This creates a computed observable which enforces a lifecycle on all values the observable is set to. When creating the activator, you can specify an initialActiveItem to activate. You can also specify a settings object. Use of the settings object is for advanced scenarios and will not be detailed much here.
A property which is the home to some basic settings and functions that control how all activators work. These are used to create the instance settings object for each activator. They can be overriden on a per-instance-basis by passing a settings object when creating an activator or by accessing the settings property of the activator. To change them for all activators, change them on the defaults property. The two most common customizations are presented below. See the source for additional information.