When a player wishes to learn about controls in his/her partner's hand, yet the player's own hand contains a void, information about aces may be worthless, because the partner may have an ace in the void suit. To compensate for the void while requesting controls, the player
(a) makes a jump to the 5 level in the suit with the void.
(b) partner then shows key cards EXCLUSIVE of any in the void suit. Responses are the same as for Roman Key Card (or Blackwood, depending upon your preference), with each step above the bid suit showing 0/3, 1/4, 2, 2 plus the queen (or 0/3, 1,2 if Blackwood).
For example, North
N E S W
1S P 3S P
5D! P 5S! P
5S shows 1 control; the Ace of Diamonds is excluded in showing controls because Partner has shown a void in that suit.