INTERFERENCE FROM OPPONENT part 1
  
 After we open and opponent interfere in level 1 we need agreements with partner from what is now the meaning of Responder's bids.
 
 Thus here we propose some rules to be follow by Responder:
 
 RULE#1: After an open in a minor suit (1
♦), independent of any interference at level 1 or 2, the asking for aces (not for keycards) will be made using the Gerber Conventions bidding 4♣ and the responses are: 4♦=zero/4 aces  4♥=1 ace, 4♠=2 aces and 4nt=3 aces.
 After the Opener response of his aces any bid by Responder is conclusive and so Opener must pass. In case of interference after 4
♣ then we use DOPI (Double zero, Pass one, next suit = 2 aces and next+1 suit = 3 aces). Examples:
 Opener Overcaller Responder (having strong hand)
   1
♦         1♠            4♣ <= Gerber – ex ♠AQ10 ♥x ♦KQ87xx ♣K98
   1
♣         1♦            4♣ <= Gerber - ex ♠KQJ ♥Kx ♦x ♣AQ98542
   1
♦         double     4♣ <= Gerber - ex ♠x ♥x ♦KQJ743 ♣AQJ82
   1
♣         double     4♣ <= Gerber - ex ♠AQ ♥x ♦KQ108 ♣KQJ987
 
 RULE#2: After an open in a minor, with or without interference at level 1 or 2, the response 4
♦ is a transfer to 4♥ showing 7/8 cards and up to 9 hcp without 2 aces and in similar way the response 4♥ is a transfer to 4♠. Examples:
 Opener Overcaller Responder
   1
♦         1♠            4♦ <= transfer to 4♥ => ♠x ♥KQJ98732 ♦J87 ♣x
   1
♣         1♦            4♥ <= transfer to 4♠ => ♠x ♥xx ♦Q87 ♣x
   1
♦         double     4♦ <= transfer to 4♥ => ♠x ♥AK987532 ♦Jx ♣Jx
   1
♣         double     4♥ <= transfer to 4♠ => ♠AKJ108xx ♥x ♦xx ♣xxx   
 
 Rule#03 - After we open in a suit at level 1 and opponent bid a takeout double our priority is to inform Opener about our strength with 10+ or less than 10 hcp and Responder do that bidding redouble or bidding anything else:
 Opener Opponent Responder
   1
♣        double     redouble <= 10+ hcp
   1
♦        double     redouble <= 10+ hcp
   1
♥        double     redouble <= 10+ hcp
   1
♠        double     redouble <= 10+ hcp
   1
♣        double     any bid up the line <= less than 10 hcp
   1
♦        double     any bid up the line <= less than 10 hcp
   1
♥        double     any bid up the line <= less than 10 hcp
   1
♠        double     any bid up the line <= less than 10 hcp
 
 Note1: after redouble all doubles are penalty, but a player should not let partner double at level 1 or level 2 when he is shorter (zero/1 card) in opponent suit principally when the opponent suit is bided by the partner of the doubler (Advancer) because in this case opponents have a 8 cards fit.
 
 Note2: of course, there are some situations that Responder even with 10 hcp should not redouble like when he bids game, splinters or shows support (like in Jordan conventions) and a strength not for punish opponents at level 1 or 2 but to play in opener's suit at level 3 or invite Opener to game.
 
 Note3: a double, after redouble, should be done when:
 1- we have more strength in honors than opponents;
 2- simultaneously we don't have support to partner's suit and presume that a misfit may occurs in this board;
 3- we have 4+ cards with good honors in the opponent suit.
 
 Rule#04 - We don't redouble having balanced hand with 4 cards support in partner's major suit or 5 cards support in partner's minor suit and we bid 2nt showing 10-11 hcp (Jordan convention):
 Opener Opponent Responder
   1
♣        double    2NT <= 10-11 hcp with 5♣+ cards
   1
♦        double    2NT <= 10-11 hcp with 5♦+ cards
   1
♥        double    2NT <= 10-11 hcp with 4♥ cards balanced hand
   1
♠        double    2NT <= 10-11 hcp with 4♠ cards balanced hand
   1
♥        double     4♥  <= undefined with 5♥+ cards
   1
♠        double     4♠  <= undefined with 5♠+ cards
   1
♥        double     3♠  <= splinter 10-11 hcp shorter in ♠ with 4♥+
   1
♥        double     4♣  <= splinter 10-11 hcp shorter in ♣ with 4♥+
   1
♥        double     4♦  <= splinter 10-11 hcp shorter in ♦ with 4♥+
   1
♠        double     4♣  <= splinter 10-11 hcp shorter in ♣ with 4♠+
   1
♠        double     4♦  <= splinter 10-11 hcp shorter in ♦ with 4♠+
   1
♠        double     4♥  <= splinter 10-11 hcp shorter in ♥ with 4♠+
  
 After Jordan (10-11 hcp) if Opener rebids his suit this is sign-off.
 
 Rule#05 - After an opening in a minor suit and a takeout double by opponent Responder bidding a suit shows 5+ cards and less than 10 hcp - not forcing, so Opener can pass with 2 cards:
 Opener Opponent Responder
   1
♣        double    1♦ <= 4♦+ and <10 hcp  ♠108xx ♥J976 ♦KQ98 ♣x
   1
♣        double    1♥ <= 5♥+ and <10 hcp  ♠Q8x ♥KJ974 ♦9xx ♣xx
   1
♣        double    1♠ <= 5♠+ and <10 hcp  ♠QJ108x ♥7 ♦Q982 ♣10xx
   1
♦        double    1♥ <= 5♥+ and <10 hcp  ♠Q7x ♥QJ972 ♦9 ♣J10xx
   1
♦        double    1♠ <= 5♠+ and <10 hcp  ♠K108xxx ♥97 ♦98 ♣Jxx   
   1
♦        double    2♣ <= 6♣+ and <10 hcp  ♠Kxx ♥972 ♦9 ♣K98xxx             
 
 Rule#06 - After an opening in a minor suit and a takeout double by opponent Responder bids 1nt with 8-9 hcp and 4333 or 4432 distribution having stoppers in both majors denying any 5 cards suit:
 Opener Opponent Responder
   1
♣        double      1NT <= 8-9 hcp  ♠K10x ♥QJ97 ♦QJ87 ♣10xx
   1
♦        double      1NT <= 8-9 hcp  ♠Q108x ♥QJ97 ♦98 ♣KJx
 
 Rule#07 - After an opening in a major suit and a takeout double when Responder strength is 6-9 hcp Responder makes a transfer to show his 6+ card suit bidding 1nt/2
♣/2♦:
 Opener Opponent Responder
   1
♠        double   1NT (trf) <= shows 6♣+ cards and 6-9 hcp
   1
♠        double   2♣   (trf) <= shows 6♦+ cards and 6-9 hcp
   1
♠        double   2♦   (trf) <= shows 6♥+ cards and 6-9 hcp
   1
♠        double   2♥   (trf) <= shows 3♠ cards and 8-9 hcp
   1
♠        double   2♠           <= shows 3♠ cards and 6-7 hcp
   1
♠        double   3♠ nVul   <= shows 4♠ cards and 3-7 hcp
   1
♠        double   3♠ Vul     <= shows 4♠ cards and 8-9 hcp
   1
♥        double   1♠           <= shows 5♠+ cards and 6-9 hcp
   1
♥        double   1NT (trf) <= shows 6♣+ cards and 6-9 hcp
   1
♥        double   2♣   (trf) <= shows 6♦+ cards and 6-9 hcp
   1
♥        double   2♦   (trf) <= shows 3♥ cards and 8-9 hcp
   1
♥        double   2♥           <= shows 3♥ cards and 6-7 hcp
   1
♥        double   3♥ nVul   <= shows 4♥ cards and 3-7 hcp
   1
♥        double   3♥ Vul     <= shows 4♥ cards and 8-9 hcp
 
 Note4: when Opener make a transfer after opponent double and Responder bids a delayed support in Opener major suit this is a constructive bid with 8-9 hcp and showing A or K in his lateral suit with 6 cards:
 Opener Opponent Responder Opponent2
   1
♠        double      1NT (trf)     pass
   2
♣         pass          2♠  <= shows 8-9 hcp and 3♠-6♣ cards
 Opener Opponent Responder Opponent2
   1
♥        double       2♣ (trf)      pass
   2
♦         pass          2♥  <= shows 8-9 hcp and 3♥-6♦ cards
 
 Resume1 - After an opening at level 1 in suit if opponent makes a takeout double the following bids are proposed for Responder:
 
 Opener Opponent Responder
  1
♣         double   pass <= waiting - less than 10 hcp
  1
♣         double   redouble <= 10+ hcp - denies 5♣+
  1
♣         double    1♦ <= 4♦ good cards or 5♦+ 6-9 hcp
  1
♣         double    1♥ <= 5♥+ with 1+ top honors and 6-9 hcp
  1
♣         double    1♠ <= 5♠+ with 1+ top honors and 6-9 hcp
  1
♣         double  1NT <= 8-9 hcp in 4333 or 4432
  1
♣         double    2♣ <= 4♣+ and 6-9 hcp
  1
♣         double    2♦ <= weak 6♦+ 1+ top honors =< 6 hcp 
  1
♣         double    2♥ <= weak 6♥+ 1+ top honors =< 6 hcp
  1
♣         double    2♠ <= weak 6♠+ 1+ top honors =< 6 hcp
  1
♣         double  2NT <= 10-11 hcp with 5♣+ cards Jordan
  1
♣         double    3♣ <= preemptive - 5♣+ cards - 6-9 hcp
  1
♣         double    3♦ <= splinter 5♣+ cards - 10-12 hcp
  1
♣         double    3♥ <= splinter 5♣+ cards - 10-12 hcp
  1
♣         double    3♠ <= splinter 5♣+ cards - 10-12 hcp
  1
♣         double  3NT <= to play - 12-15 hcp
  1
♣         double    4♣ <= Gerber - asking for aces
  1
♣         double    4♦ <= transfer to 4♥ - 7♥+ cards
  1
♣         double    4♥ <= transfer to 4♠ - 7♠+ cards
  1
♣         double    5♣ <= to play
 
 Opener Opponent Responder
  1
♦         double   pass <= waiting - less than 10 hcp
  1
♦         double   redouble <= 10+ hcp - denies 5♦+
  1
♦         double    1♥ <= 5♥+ with 1+ top honors and 6-9 hcp
  1
♦         double    1♠ <= 5♠+ with 1+ top honors and 6-9 hcp
  1
♦         double  1NT <= 8-9 hcp in 4333 or 4432
  1
♦         double    2♣ <= 6♣+ and 6-9 hcp
  1
♦         double    2♦ <= 4♦+ 6-9 hcp
  1
♦         double    2♥ <= weak 6♥+ 1+ top honors =< 6 hcp
  1
♦         double    2♠ <= weak 6♠+ 1+ top honors =< 6 hcp
  1
♦         double  2NT <= 10-11 hcp with 5♦+ cards
  1
♦         double    3♣ <= weak 6♣+ 1+ top honor =< 6hcp
  1
♦         double    3♦ <= preemptive 5♦+ cards - 6-9 hcp
  1
♦         double    3♥ <= splinter 5♣+ cards - 10-12 hcp
  1
♦         double    3♠ <= splinter 5♣+ cards - 10-12 hcp
  1
♦         double  3NT <= to play - 12-15 hcp
  1
♦         double    4♣ <= Gerber - asking for aces
  1
♦         double    4♦ <= transfer to 4♥ - 7♥+ cards
  1
♦         double    4♥ <= transfer to 4♠ - 7♠+ cards
  1
♦         double    5♦ <= to play 
 
 Opener Opponent Responder
  1
♥         double   pass <= waiting - less than 10 hcp
  1
♥         double   redouble <= 10+ hcp - denies 4♥+ cards
  1
♥         double    1♠ <= 5♠+ with 1+ top honors and 6-9 hcp
  1
♥         double  1NT <= transfer to 2♣ - 6♣+ cards 6-9 hcp
  1
♥         double    2♣ <= transfer to 2♦ - 6♦+ cards 6-9 hcp
  1
♥         double    2♦ <= 3♥ cards - 8-9 hcp 
  1
♥         double    2♥ <= 3♥ cards - 6-7 hcp
  1
♥         double    2♠ <= weak 6♠+ 1+ top honors <= 6 hcp
  1
♥         double  2NT <= 10-11 hcp with 4♥ cards balanced
  1
♥         double    3♣ <= weak 6♣+ 1+ top honors <= 6 hcp
  1
♥         double    3♦ <= weak 6♦+ 1+ top honors <= 6 hcp
  1
♥         double    3♥ <= 4♥ cards - 6-9 hcp (Vul ?)
  1
♥         double    3♠ <= splinter 4♥+ cards and 9-11 hcp
  1
♥         double  3NT <= to play - 12-15 hcp
  1
♥         double    4♣ <= splinter 4♥+ cards and 9-11 hcp
  1
♥         double    4♦ <= splinter 4♥+ cards and 9-11 hcp
  1
♥         double    4♥ <= to play - 5♥+ cards
  
 Opener Opponent Responder
  1
♠         double   pass <= waiting - less than 10 hcp
  1
♠         double   redouble <= 10+ hcp - denies 4♠+ cards
  1
♠         double  1NT <= transfer to 2♣ - 6♣+ cards 6-9 hcp
  1
♠         double    2♣ <= transfer to 2♦ - 6♦+ cards 6-9 hcp
  1
♠         double    2♦ <= transfer to 2♥ - 6♥+ cards 6-9 hcp 
  1
♠         double    2♥ <= 3♠ cards - 8-9 hcp
  1
♠         double    2♠ <= 3♠ cards - 6-7 hcp
  1
♠         double  2NT <= 10-11 hcp with 4♠ cards balanced
  1
♠         double    3♣ <= weak 6♣+ 1+ top honors =< 6 hcp
  1
♠         double    3♦ <= weak 6♦+ 1+ top honors =< 6 hcp
  1
♠         double    3♥ <= weak 6♥+ 1+ top honors =< 6 hcp
  1
♠         double    3♠ <= 4♠ cards and 6-9 hcp (Vul ?)
  1
♠         double  3NT <= to play - 12-15 hcp
  1
♠         double    4♣ <= splinter 4♠+ cards and 9-11 hcp
  1
♠         double    4♦ <= splinter 4♠+ cards and 9-11 hcp
  1
♠         double    4♥ <= splinter 4♠+ cards and 9-11 hcp
  1
♠         double    4♠ <= to play - 5♠+ cards
 
 Resume2 – After an opening in 1
♣ if opponent interfere at level 1 the propose Responder`s bids are:
 
 Responder Opponent Opener Opponent
 ...............................    1
♣         1♦          
     ?
  pass    <= waiting - may have
♦ suit or less than 6 hcp
 double <= shows 6+ hcp and both major 4
♥5♠
    1
♥     <= shows 6+ hcp and 4♥+ cards
    1
♠     <= shows 6+ hcp and 4♠+ cards
    1NT   <= 8-10 hcp and 1,5 stopper in
♦ denies majors
    2
♣     <= 4♣+ cards and 6-9 hcp - good clubs support
    2
♦     <= invitation 5♣+ and 11+ hcp denies majors
    2
♥     <= weak less than 6 hcp and 6♥+ with 1 top honor A/K
    2
♠     <= weak less than 6 hcp and 6♠+ with 1 top honor A/K
    2NT   <= invitation 11 hcp with 1,5 stopper no majors
    3
♣     <= preemptive 5♣+ and 6-9 hcp - no majors
    3
♦     <= asking for stopper in ♦ Opener bid 3nt or 4♣/5♣
    3
♥     <= splinter 5♣+ cards and 11-12 hcp singleton ♥
    3
♠     <= splinter 5♣+ cards and 11-12 hcp singleton ♠
    3NT   <= to play - 12-15 hcp and 1,5 stopper in
♦
    4
♣     <= Gerber - ask for aces - strong hand GF
    4
♦     <= transfer to 4♥ => ♠x ♥KQJ98732 ♦J87 ♣x
    4
♥     <= transfer to 4♠ => ♠AQJ987xx ♥J2 ♦7 ♣xx
    5
♣     <= to play => ♠Kx ♥32 ♦7 ♣KQ876xxx
 
 Responder Opponent Opener Opponent
 ...............................    1
♣         1♥           
     ?
  pass    <= waiting - may have
♥ suit or less than 6 hcp
 double <= shows 4
♠ and 6+ hcp
    1
♠     <= shows 5♠+ cards and 6+ hcp
    1NT   <= 8-10 hcp and 1,5 stopper in
♥ denies 4 spades
    2
♣     <= 4♣+ cards and 6-9 hcp deny Spades
    2
♦     <= 5♦+ cards and 10+ hcp - one-round force
    2
♥     <= invitation 11+ hcp and 5♣+ denies 4 spades
    2
♠     <= weak less than 6 hcp and 6♠+ with 1 top honor
    2NT   <= invitation 10-12 hcp with 1,5 stopper no majors 
    3
♣     <= preemptive 5♣+ and 6-9 hcp - no majors
    3
♦     <= splinter 5♣+ cards and 10-11 hcp singleton ♦
    3
♥     <= asking for stopper in ♥ for bid 3nt or 4♣/5♣  
    3
♠     <= splinter 5♣+ cards and 11+ hcp singleton ♠
    3NT   <= to play - 12-15 hcp and 1,5 stopper in
♦
    4
♣     <= Gerber - ask for aces - strong hand GF
    4
♥     <= transfer to 4♠ => ♠AKJ9xxxx ♥J2 ♦7 ♣xx 
    5
♣     <= to play
 
 Responder Opponent Opener Opponent
 ...............................    1
♣         1♠           
     ?
  pass    <= waiting - may have
♠ suit or less than 6 hcp
 double <= shows 4
♥+ cards and 6+ hcp
    1NT   <= 8-10 hcp and 1,5 stopper in
♥ denies 4 hearts
    2
♣     <= 4♣+ cards and 6-9 hcp denies 4 hearts
    2
♦     <= 5♦+ cards and 10+ hcp - on-round force
    2
♥     <= 5♥+ cards and 10+ hcp - one-round force
    2
♠     <= invitation 5♣+ and 11+ hcp - one-round force
    2NT   <= invitation 11-12 hcp with 1,5 stopper no hearts
    3
♣     <= preemptive 5♣+ and 6-9 hcp - no majors
    3
♦     <= splinter 5♣+ cards and 11+ hcp singleton ♦
    3
♥     <= splinter 5♣+ cards and 11+ hcp singleton ♥  
    3
♠     <= asking for stopper in ♠ bidding 3nt or 4♣/5♣   
    3NT   <= to play - 12-15 hcp and 1,5 stopper in
♠
    4
♣     <= Gerber asking aces - strong hand GF
    4
♦     <= transfer to 4♥ => ♠x ♥KQJ98732 ♦J87 ♣x
    5
♣     <= to play
 
 Resume3 - After an opening in 1
♦ if opponent interfere bidding a major at level 1 the Responder`s bids proposed are:
 
 Responder Opponent Opener Opponent
 ...............................    1
♦         1♥     
     ?
  pass    <= waiting - may have
♥ suit or less than 6 hcp
 double <= shows 4
♠ and 6+ hcp
    1
♠     <= shows 5♠+ cards and 6+ hcp
    1NT   <= 8-10 hcp and 1,5 stopper in
♥ denies 4 spades
    2
♣     <= 5♣+ cards and 10+ hcp - one-round force
    2
♦     <= 4♦+ cards and 6-9 hcp
    2
♥     <= invitation 11-12 hcp and 4♦+ denies 4 spades
    2
♠     <= weak less than 6 hcp and 6♠+ with 1 top honor A/K
    2NT   <= invitation 11-12 hcp with 1,5 stopper no majors
    3
♣     <= preemptive 6♣+ cards and 6-9 hcp - no majors
    3
♦     <= preemptive 5♦+ cards and 6-9 hcp 
    3
♥     <= ask for stopper in ♥ bidding 3nt or 4♦ or 5♦  
    3
♠     <= splinter 5♦+ cards and 10-11 hcp singleton ♠
    3NT   <= to play - 12-15 hcp and 1,5 stopper in
♥
    4
♣     <= Gerber asking aces - strong hand GF
    4
♥     <= transfer to 4♠ => ♠KQJ987xx ♥2 ♦J7 ♣xx
    5
♦     <= to play
 
 Responder Opponent Opener Opponent
 ...............................    1
♦         1♠           
     ?
  pass    <= waiting - may have
♠ suit or less than 6 hcp
 double <= shows 4
♥+ cards and 6+ hcp
    1nt   <= 8-10 hcp and 1,5 stopper in
♥ denies hearts
    2
♣     <= 5♣+ cards and 10+ hcp - one-round force
    2
♦     <= 4♦ cards and 6-9 hcp - denies hearts
    2
♥     <= 5♥+ cards and 10+ hcp - one-round force
    2
♠     <= invitation 5♣+ and 11+ hcp - one-round force
    2nt   <= invitation 10-12 hcp with 1,5 stopper no hearts
    3
♣     <= preemptive 5♣+ and 6-9 hcp - no majors
    3
♦     <= splinter 5♣+ cards and 10-11 hcp singleton ♦
    3
♥     <= splinter 5♣+ cards and 10-11 hcp singleton ♥  
    3
♠     <= asking for stopper in ♠ bidding 3nt else rebid ♣  
    3nt   <= to play - 12-15 hcp and 1,5 stopper in
♠
    4
♣     <= Gerber asking aces 4♥=1/4♠=2/4nt=3
    4
♦     <= transfer to 4♥ => ♠x ♥AKJ98732 ♦10 ♣10xx
    5
♣     <= to play
 
 Resume4 - After an opening in 1
♥ if opponent interfere with 1♠ the Responder`s bids proposed are:
 
 Responder Opponent Opener Opponent
 ...............................    1
♥         1♠     
     ?
  pass    <= waiting - may have long spades
 double <= 6+ hcp and both minors
  1NT    <= 8-10 hcp and 1,5 stopper in
♥ denies 4 spades
    2
♣     <= 5♣+ cards and 10+ hcp - one-round force
    2
♦     <= 5♦+ cards and 10+ hcp - one-round force
    2
♥     <= 3♥ cards support and 6-9 hcp
    2
♠     <= invitation 10-11 hcp and 3♥ cards
  2NT    <= invitation 11-12 hcp with 1,5 stopper in Spades
    3
♣     <= preemptive 6♣+ cards and 6-9 hcp
    3
♦     <= preemptive 6♦+ cards and 6-9 hcp 
    3
♥     <= 4♥ cards and 6-9 hcp (Vul ?)  
    3
♠     <= splinter 4♥+ and 11+ hcp
  3NT    <= to play - 12-15 hcp and 1,5 stopper in
♥
    4
♣     <= splinter 4♥+ and 11+ hcp
    4
♦     <= splinter 4♥+ and 11+ hcp
    4
♥     <= to play 4♥+ and 2-10 hcp
  4NT     <= RKB1430 for
♥

Bottom Line: Even after an opponent takeout double or overcall partnership may create reliable information to have better decision in the board.