ACOL
This is a standard bidding system used predominantly by the British, but is also widely used throughout the world. The system was devised by Maurice Harrison-Gray, Iain Macloed, J.C.H. Marx, Terence Reese and S.J.Simon. The system got its named from the street name of the North London club where it was first played in 1934. The basis for the system were the early writings of Ely Culbertson.
The main features of the system are:
- Weak NT when not-vulnerable, Strong NT when vulnerable;
- Strong 2
; - Strong Twos;
- Limit Raises;
- 4-card Majors;
- Fourth Suit Forcing;
- Gambling 3NT;
- Ace asking 4NT Opening;
- Jump rebids are not forcing unless in a new suit.