Jordan 2 NT (Truscott 2 NT)
Developed by Alan Truscott, but it is spreadly known as Jordan NT since it is presented and popularized in United States by Robert F.Jordan.
When a major openning is doubled, responder shows a limited support by bidding 2 NT with generally 9-12 points and 3-4 cards support. Opener may rebid the major in 3rd or 4th level or may declare a second suit for game or slam research according his openning value. This convention is mostly used by the two over one players who apply the jump support in preemptive manner with 0-8 points against opponents' overcall. If there is no overcall then jump support will show a limited raise with 9-12 points.