from 12 -15 hp or 26-31 zp,
Answers - undisturbed
The continuation happens in a natural way, except for 1NT (see Duke below) and 2♣ (relay)
OM : openingsmajor
AM : other mjaor than the OM
RF : forcing for a roundd
NF : non forcing
c : card
hp : honnour points
sn : singleton
w/ : with
The DUKE convention for a major opening
The partner who starts Duke -1NT- has a sn or void in OM, else he would have bid 2OM.
The opener must bid 2♣ unless he has a sn ♣ to avoid that partner would probably pass out.
With a 6 card in OM, the opener can bid 2OM willing to play in a 6-1 fit.
Also a 4 card AM is not let unbid in order to safeguard a possible -4 fit in AM.
Without a 6c OM, without a 4c AM, but with a sn♣ , the opener will bid 2♦.
After 2♣, with at least a 2c ♣, the partner shows the reason for his action :
(after 1♠ ) : 2♥
RF, 10+,any distribution
except ♣ (2)
NF,5+c, < 10hp
10-11hp, no 3c M
(1) The sequence 1M-2♣-2♦ deserves special attention. Unlike the situation of a maximal answer where a 4 card minor can be named is here the id of the minor unknown. If required, the partner can investigate by bidding 2AM, an "impossible" bid to be natural understood. Indeed, a 4card AM is useless as opener has denied this. A 5card AM is also impossible because this would have been bid directly. Ergo, 2AM conventionnally asks for the id of the minor. The answer is with steps and reveals more :
s12 = ♣/♦ in a 54xx s34 = ♣/♦ in a 5431 with a sn in am s56 = ♣/♦ in a 5431 with a sn in AM s78 = ♣/♦ in a 56xx
(2) When opener holds a 4 card AM or 6 card OM, it is not unlikely to find a sn in that hand . Partner can investigate via 3♣. The answer iss via steps s1234 : no sn/ ♣/♦ /AM.
Also, after a 2/3 NT rebid (5332), partner can ask with 3/4♣ the id of the doubleton. Answer = s123 = ♣/♦ /AM.
(3) When a 1M opener rebids minimum ( 2AM/OM) the partner knows enough to either pass or after 2AM go back to the OM suit or to bid the game contract. Therefore, if partner bids 3AM or 3OM, he shows slem ambition. The opener continues with controls.
Also after a maximal answer (3-level) a game contract is sure. Not bidding that game contract shows slem ambition and starts up control bids.
Eg. 1M - 2♣
3x - 3x+1 (or 4♣ after 3♠)
When opponents overcall 1M
In general , we play SYSTEM OFF, continuing in a natural way.
Only after a double intervention, we play TRUSCOTT :
2♣ becomes natural, NF,5 c♣ , sn OM
2NT = 10-11hp and 3+c OM
Jazz raises remain valid.