From Valve Developer Community
A prefab located in the Prefabs HL2 folder, containing a setup for a scripted movement of a Combine scanner.
This prefab contains the following:
- An npc_cscanner NPC template to be spawned.
- An npc_template_maker entity to spawn it.
- Three path_corner entities that will mark the path for the scanner to follow.
- An aiscripted_schedule entity that will make the scanner move to the first path_corner when spawned.
The prefab is started by sending a Spawn signal to the npc_template_maker from an external source.