Imperial Code 16 was a communications code used by Imperial droids, and often indicated that they were in standby mode. When Rebel astromech droid Chopper used the code on a journey back from a mission to Killun Station to steal Imperial codes, former Imperial protocol droid AP-5 took it as a sign that Chopper had been compromised while on the mission: he had in fact been hijacked by Imperial controller LT-319 in an attempt to find out the location of the Phoenix Cell's base.