During this phase you can deploy any unloaded devices in the sectors that they occupy.  When a device is deployed, it is considered to be activated even if its effect is not registered until a later phase, and any empire in the same sector will register that activation on short-range scanners.  Empires in nearby sectors will not be able to see the device deployment directly, but they may be able to infer its use from its effects.  One-shot devices are destroyed immediately when they are deployed.  Persistent devices remain active until they are destroyed or loaded.
 
A device deployed in the same sector as an operational starbase (friendly or otherwise) will not function.  A persistent device deployed in the same sector as a starbase is simply unloaded and not deployed (and can be loaded and redeployed later).  A one-shot device deployed in the same sector as a starbase is unloaded and destroyed without being activated.