Source: www.bridgeinchicago.com by  Morton Miller        I play controls with some of my partners in response to a 2opener. A king is one control and an ace is two controls. A response of 2shows no ace, zero or one king. A response of 2 shows either one ace or two kings. A response of 2 shows one ace and one king. A response of 2 no trump shows three kings. A response of 3 shows either two aces, one ace and two kings, or four kings, and so on. So if I open 2 and you bid 2, you have either zero or one king and no ace. Now if I bid 4 No Trump, I want to know if you have a king. If you don’t bid 5; if you do you bid 5. If I open 2 and you bid 2, I want to know if you have an ace. If you have an ace, bid 5. If you have no aces, bid 5 (therefore you have two kings). If I open 2 and you bid 2, I know that you have an ace and a king, so if I bid No Trump I am asking you for queens. You respond 5 with none, 5 with one, 5 with two, etc. I open 2 and you bid 2NT, I know you have no ace and three kings, so if I bid No Trump you bid your queens, 5 for no queen, etc. If I open 2 and you bid 3, bid your aces, 5 for none, 5 for one, etc. DOPI can also come up with interference. If I open 2 and LHO bids a suit, e.g. 2, a double by you shows no control, pass shows one king, 2 shows one ace or two kings, etc. So if I then bid No Trump after you bid 2 or higher, tell me how many aces you have. Here are some examples of your response after I open 2:
1. You bid 2; I bid 4NT. You have 542 653 K53 7654.What do you bid?
2. You bid 2. I bid 4NT. You have K32 743 8642 K53. What do you bid?
3. You bid 2. I bid 4NT. You have K62, QT4, A764, Q62.
4. You bid 2NT. I bid 4NT. You have K43, Q432, K752, K3. What do you bid?
5. You bid 3. I bid 4NT. You have K532, K75, K3, K875. What do you bid?
6. You bid 3. I bid 4NT. You have A6, K732, K653, KT9. What do you bid?
7. I bid 2. You have A75, A653, A42, A96. What do you bid?

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Here are some examples of your response after I open 2:
1. You bid 2; I bid 4NT. You have 542 653 K53 7654.What do you bid?
2. You bid 2. I bid 4NT. You have K32 743 8642 K53. What do you bid?
3. You bid 2. I bid 4NT. You have K62, QT4, A764, Q62.
4. You bid 2NT. I bid 4NT. You have K43, Q432, K752, K3. What do you bid?
5. You bid 3. I bid 4NT. You have K532, K75, K3, K875. What do you bid?
6. You bid 3. I bid 4NT. You have A6, K732, K653, KT9. What do you bid?
7. I bid 2. You have A75, A653, A42, A96. What do you bid?
Answers : 1. 5 2. 5 3. 5 4. 5 5. 5 6. 5 7. I’d try 7NT.