This is an interesting convention that has some clear advantages and is similar to transfers after a 1NT opening. I've seen descriptions of a few variations but nothing "authoritative". Here I'll describe one that is simple and can be tacked on to your existing methods without much disruption.
When you open one club and next hand passes, partner may respond as follows:
1♦ Replaces the 1♥ response 1♥ Replaces the 1♠ response 1♠ Replaces the 1♦ and 1NT responses (5+ diamonds, or 6-10 HCP balanced without a major) 1NT Balanced, no major, good 10 to bad 12 HCP, nonforcing 2NT Balanced, no major, game forcing, could have slam interest Other Same as your current methodsAll this is on if second hand doubles or overcalls 1♦ or 1♥ (double replaces those bids). It's off with any higher overcall.
Opener rebids naturally, with some special considerations.
When the response is 1♦ or 1♥, accepting the transfer at the 1-level shows exactly three-card support. With 4-card support you would accept at the 2-level or higher as appropriate for your strength. Other nonforcing bids deny support and are otherwise normal according to your methods. Bidding proceeds normally.
Some examples after a 1♦ response:
1♣ 1♦ 1♥ 3 hearts exactly, responder may pass with a bare minimum 1♠ 4 spades, not 3 hearts 1NT 12-14 balanced, not 3 hearts or 4 spades 2/3/4♥ 4 hearts, natural Other Same as your current methods after a 1♥ responseNew Minor Forcing (diamonds) or some other checkback is still useful after responder shows a major and opener rebids 1NT, because you may want to check for the other major or create a forcing sequence with a 4+ card minor suit. You should make this mostly consistent with your methods after a 1♦ opening.
After a 1♠ response you would rebid as you normally would knowing that partner does not have a major. If partner continues then he is showing primary diamonds in addition to the bid suit. Here are some examples that may vary according to your normal methods:
1♣ 1♠ 1NT Pass The strong hand declares! 2♣ Diamonds and clubs, nonforcing 2♦ 6-10 HCP with long diamonds 2♥/♠ 2-suited with diamonds, game force 2NT Diamonds, artificial game force (not natural because the 1NT response is for that) 3♣ Diamonds and clubs, invitational (like standard 1♣ - 1♦ - 1NT - 3♣) 3♦ Diamonds, invitational (like standard 1♣ - 1♦ - 1NT - 3♦) 3♥/♠ Whatever these would mean for you after a natural 1♣ - 1♦ - 1NT 3NT To play, ambiguous 1♣ 1♠ 2♣ 2♦ 6-10 HCP with long diamonds 2♥/♠ 2-suited with diamonds, game force 2NT Diamonds, artificial game force (not natural because the 1NT response is for that) 3♣ Diamonds and club support, invitational (like standard 1♣ - 1♦ - 2♣ - 3♣) 3♦ Diamonds, invitational (like standard 1♣ - 1♦ - 2♣ - 3♦) 3♥/♠ Whatever these would mean for you after a natural 1♣ - 1♦ - 2♣Support doubles are recommended for dealing with overcalls by third hand after a 1♦ or 1♥ response or equivalent double. For example: 1♣ - (1♥) - Dbl - (2♥) - Dbl shows 3-card support for partner's spades.
That's about it. Advantages are that the strong hand ends up declaring more often, 5-3 major fits are easily found, competitive bidding is more effective and 2NT contracts are more often avoided. I cannot think of any disadvantages!
As best I can tell this is legal for all ABF events, as system regulations are mostly about the meanings of opening bids. It does not appear to be permitted in ACBL events with masterpoint limits. And of course these methods should be pre-alerted.
Suggested Defence
If opponents ask for a suggested defence, or if they use this convention themselves, try this:
- Over the 1♦ or 1♥ response bid as if responder had bid 1♥ or 1♠ respectively. A one-level bid of the suit shown would be a cue-bid, so Michaels if you play that.
- Over the 1♠ response double as takeout for the majors or a strong hand, otherwise bid naturally.