Hi Helene,

The definition of "could be under an opening hand" or "could be same strength" is not strong enough of a definition to prevent Unauthorised Information. Stayman and Transfers could be up to 18ish.

Imagine a filing cabinet that contains all the possible hands in bridge grouped by how many HCP they have. After you pass out of turn you have generated the information that you are in the 0-11 hcp range. This grouping of hands (minus the group of hands that you would open a weak 2/3/4) is the set of all hands that you have shown. When you now get to make a call, a comparable call can not include hands from outside of that set. It can furthur reduce the size (say pass show 0-4) which will be fine, but anything like a transfer or stayman is unlimited and so includes all 12+hcp that your hand is known not to be. 

You can make any legal call you want however the following condition will apply.

If your call includes hands that were not in the set, then the call is not comparable. As it's not comparable, partner will have to pass for the rest of the auction. 

If you call does not include hands that were not in the set, then the call is comparable and there is no problem.

Bids like 3NT or 4M show not enough for slam 0-10ish and to play so these are comparable. If you never bid 4NT Quant on 12hcp then that would also be comparable as it will show 10-11hcp and inv to 6NT. But thats about it. 

If you choose one of the non-comparable options then the director asses damages at the end. For instance if you choose 3D which would normally be a transfer and now must be passed. You have obtained a result which would not normally be possible and so the director can adjust the board when required. 

Hopefully this helps.

Jack James

Thank you James but what do  you mean by this line please?

"If your call includes hands that were not in the set, then the call is not comparable. As it's not comparable, partner will have to pass for the rest of the auction."

I was under the impression that if I do not make a comparable call, my partner must pass ONLY ONCE...is that not right?

Thank you

Helene

Yes, my bad.

For inadmissable doubles and redoubles it's pass for the rest of the auction. Here your partner only has to pass for one round (although as they opened 2NT that is likely to be the rest of the auction). 

Cheers,

Jack

thank you James