DFC:
Taking a class D zone as an example, the service provided would either be an approach control service or aerodrome control service as appropriate
Thank you, at least someone's been paying attention! All the posts in here about ATC offering a Basic Service inside CAS are, pardon the pun, BS. When did anyone ever get a FIS inside CAS? For the same reason (i.e. it's a service which is only available outside CAS), you cannot get a BS inside CAS. The clue is in what controllers at units inside controlled airspace will tell you when you call them up from outside their zone asking for a transit e.g. "it's a Basic Service outside controlled airspace".
NS