After a suit change at level 2 rebid by opener
there are 4 types of rebids after a forcing NT initialresponse:
-0 Pass with 5-8 HCP and nothing better to say
-1 Support in Opener's 1st suit
at the 2 level with 5-10HCP and 2 cards in opening suit
at the 3 level with 3 cards in Opener’s Suit and 10-12HCP
-2 Support in Opener's 2nd suit at the 3 levelwith a 4-5+ fit in Opener’s 2nd Suit and 10-12 useful HCP
-3 A suit shift
at the 2 level with no fit, a weak hand (5 – 9 HCP) and a 5-6+ card suit. This is a sign off. Opener will pass
at the 3 level with a top range 1NT (10 – 11HCP) and a good 6+ card suit. This bid is invitational but not forcing . Opener may pass or seek a NT contract.
-4 A NT bid
at minimum level.... Strength can be shown in later bidding.