ERKCB♣ ♥ ♠ ♦
This is Extended Roman Key Card Blackwood.
The four usual responses to a RKCB are exactly the same in ERKCB!
So here are our complete ERKCB responses:
- 5♣ 3 or 0 Key cards
- 5♦ 4 or 1 Key cards
- 5♥ 2 Key cards
- 5♠ 2|4 Key cards & the Queen of trumps
- 5N 3 Key cards & the Queen of trumps
- 6♣ 1 Key card & a useful void (a Key card may be a critical Q)
- 6♦ 2 Key cards & a useful void (a Key card may be a critical Q)
In the case where a double fit has been expressed there are actually 7
key cards! and 2 Key Queens! Now the 4N bidder must possess at lest 2KCs. The regular responses to 4N should be
preferred in this case even if using the variant above and 5♥ modified
to read 2|5 key cards! & 5N modified to 3|5