[mikl_plkcc]

I am playing some games and the system there says system on after doubling a 1NT, e.g. (1NT) - X (penalty) - (/) - 2♥ is transfer to ♠. Is this convention commonplace?

I think I have also seen system on after a 2NT rebid (not after a strong 2♣ opening) but I can't remember the exact sequence. How does it work?

[jdiana]

1. We played systems on after X. I think that is pretty standard. After 2♣, X was Stayman but otherwise, systems were on there also. (If 2♣ shows both majors, then X is no longer Stayman. In that case, we used our simplified lebensohl bids.) I think that's also fairly common but I'm not sure.

2. After 1x-1y-2NT (18-19 HCP), if that's what you're referring to, we played systems off.

[mycroft]

If you mean "systems on after they double our 1NT", that's an okay decision that many (playing strong NT at least) play. Why give up all your hard-learned system just because they said something you can ignore, especially because many if not most pairs play a conventional double?

If you mean "systems on after we double their 1NT" (for penalty), run. Do not even look. First, the best penalty doubles are where you can lead your fourth-best J of 7, or the similar "one-loser suit with an ace". If this gets pulled, I know where to play and you don't. Second, you should not be planning on pulling 1NTx (enough to have lots of system against it). You pull in two situations: "I'm too weak to sit for this, and I have a long suit that will score many more tricks as trump than on defence" and "I don't think we are getting this enough to beat our likely game, when we can place all the outstanding high cards". The first means you want to be able to play 2♣, not 3♣, if that's the suit; the second is so rare you can assign 2NT to it and "guess" your way to game.

Plus, I guarantee that at least half the time, one of you will forget, or think you're playing it when partner is saner, and that invariably leads either to a poor score or a director-assigned (poor) score.

[pescetom]

1. I agree that systems on after their penalty X is common, as is X of their 2♣ being Stayman (although I don't think that is great when 2♣ is Landy, as it almost always is over here).

2. After 1X - 1Y; 2NT some of our old timers play systems on, but I don't think it is common (or very good).
After preparatory sequences to NT like 1♦(5+) - 1M(3+); 1NT(18-19) or 2♦(Multi) - 2M(pass/correct); 2NT(20-21) then systems are obviously on.

[jdiana]

mycroft, on 2025-February-14, 08:06, said:

If you mean "systems on after they double our 1NT", that's an okay decision that many (playing strong NT at least) play. Why give up all your hard-learned system just because they said something you can ignore, especially because many if not most pairs play a conventional double?

If you mean "systems on after we double their 1NT" (for penalty), run. Do not even look. First, the best penalty doubles are where you can lead your fourth-best J of 7, or the similar "one-loser suit with an ace". If this gets pulled, I know where to play and you don't. Second, you should not be planning on pulling 1NTx (enough to have lots of system against it). You pull in two situations: "I'm too weak to sit for this, and I have a long suit that will score many more tricks as trump than on defence" and "I don't think we are getting this enough to beat our likely game, when we can place all the outstanding high cards". The first means you want to be able to play 2♣, not 3♣, if that's the suit; the second is so rare you can assign 2NT to it and "guess" your way to game.

Plus, I guarantee that at least half the time, one of you will forget, or think you're playing it when partner is saner, and that invariably leads either to a poor score or a director-assigned (poor) score.

Oh, right! I think I misread the OP's question.

Larry Cohen does suggest the "systems on" approach for a penalty double of a weak notrump opening - https://www.larryco....-vs-notrump-556

[P_Marlowe]

#1 playing a penalty double against a strong NT is, ok, the robots play it, but it may
not be very common. If you play in groups, that regular psych a strong NT, the penalty X
has some attraction.

#2 If we make a penalty double against their strong NT, playing the same system, one plays,
when having opened 1NT is not bad, it seemed reasonable when I heard about this treatment.
Most of the time you will pass the X, either with conviction, or due to a lack of an alternative.
Having a way to scramble to 2M via a stayman inquiry is not bad, it will be useful some of time.
Is it common? I guess not. But than again, it is a rare seq., the freq. is pretty low, as long
as you are certain, that you and your p know, what they are play, you will be ok.

Keep in mind, I dont play a penalty X against a strong NT, not even against a weak NT.

[pescetom]

 mycroft, on 2025-February-14, 08:06, said:

If you mean "systems on after we double their 1NT" (for penalty), run. Do not even look. First, the best penalty doubles are where you can lead your fourth-best J of 7, or the similar "one-loser suit with an ace". If this gets pulled, I know where to play and you don't. Second, you should not be planning on pulling 1NTx (enough to have lots of system against it). You pull in two situations: "I'm too weak to sit for this, and I have a long suit that will score many more tricks as trump than on defence" and "I don't think we are getting this enough to beat our likely game, when we can place all the outstanding high cards". The first means you want to be able to play 2♣, not 3♣, if that's the suit; the second is so rare you can assign 2NT to it and "guess" your way to game.

Plus, I guarantee that at least half the time, one of you will forget, or think you're playing it when partner is saner, and that invariably leads either to a poor score or a director-assigned (poor) score.

I would run from playing double of strong NT as penalty, it was a long term loser in my experience (unlike our current agreement to promise a 4M5m).
But if one plays it, I agree that playing systems on is not a great idea, even if your systems allow you to play in 2♦ as ours do. Being able to scramble to 2M is probably worth as much as being able to play 2♣, but natural bidding has the advantage of putting the opener on lead (not huge here, but still).