Originally Posted by Check Essential

You are pretty much correct but you have to be careful when you say "30 hours off". You're still on call but just unusable until you've had rest.

They do not have to assign rest but they can't assign you duty if you haven't had legal rest.
ie => if they let you go "illegal" then you essentially have a 30 hour leash instead of 12.

They will assign rest by contacting you in the same method as when they assign trips. 1) pre-release schedule check 2) phone call 3) attempted phone call.
If #3 then there's a couple special rules:

such rest period shall begin no earlier than 2 hours following the first attempted contact. In such case, the pilot must inform the Company within 9 hours of first attempted contact if he was unable to begin his rest as scheduled.