Source: www.bridgeinchicago.com by Morton Miller
I play controls with some of my partners in response to a 2

opener. A king is one control and an ace is two controls. A response of 2

shows 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

:
- You bid 2
; I bid 4NT. You have
542
653
K53
7654.What do you bid?
- You bid 2
. I bid 4NT. You have
K32
743
8642
K53. What do you bid?
- You bid 2
. I bid 4NT. You have
K62,
QT4,
A764,
Q62.
- You bid 2NT. I bid 4NT. You have
K43,
Q432,
K752,
K3. What do you bid?
- You bid 3
. I bid 4NT. You have
K532,
K75,
K3,
K875. What do you bid?
- You bid 3
. I bid 4NT. You have
A6,
K732,
K653,
KT9. What do you bid?
- 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

:
- You bid 2
; I bid 4NT. You have
542
653
K53
7654.What do you bid?
- You bid 2
. I bid 4NT. You have
K32
743
8642
K53. What do you bid?
- You bid 2
. I bid 4NT. You have
K62,
QT4,
A764,
Q62.
- You bid 2NT. I bid 4NT. You have
K43,
Q432,
K752,
K3. What do you bid?
- You bid 3
. I bid 4NT. You have
K532,
K75,
K3,
K875. What do you bid?
- You bid 3
. I bid 4NT. You have
A6,
K732,
K653,
KT9. What do you bid?
- 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.