INTERFERENCE
SAYC by Ned Downey

If RHO doubles partner's 1NT call, all systems are "on "  and "2C is Stayman", 2D and 2H are transfers, etc.

If RHO bids over partner's 1NT call, all systems are off, though a reasonable approach (by partnership agreement) would be

If RHO bids 2C over partner's 1NT call, Double is Stayman and all other systems remain "on".

If RHO bids 2D, 3D is Stayman, Double is a transfer to hearts and all other systems remain "on".

If RHO bids 2H or higher, a cue bid of the overcalled suit is Stayman (game forcing). All other systems are off. Suit bids are natural.

If Stayman is doubled, opener may:

  • Make a normal rebid
  • Pass with four clubs
  • Redouble with five clubs (or four good ones)

If Stayman is overcalled, opener may:

  • Bid a four-card major at the two level
  • Double for penalty (with four or more cards in the opponent's suit)
  • Pass
  • In any event, responder may:
    • Double (for penalty)

      Pass

      Make a normal rebid.

If a transfer is doubled, opener may:

  • Pass. In this event, responder may:
    • Pass, to play

      Redouble, to play

      Make a normal bid

      Signoff by bidding his major at the two-level

  • Redouble (showing a strong holding in the doubled suit)
  • Complete the transfer (showing three+ trumps)
  • Accept the transfer at the three-level (showing four trump and a maximum)

If a transfer is overcalled, opener may:

  • Bid three of the major (with a good supporting hand)
  • Double (for penalty)
  • Pass. In this event, responder may:
    • Re-transfer

      Make a normal bid

      Double (to show strength)

      Pass