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:

Note: 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