In Competition

1♣ - (1♦/♥) - 

dbl    =    transfer to ♥/♠

        after 1♣ - (1♦) if OP bids 2♣, RE with ♦ ST bids 2NT instead of otherwise compulsory 2♦

3♥/♠    =    preemptive 7(6)+ cards

other    =    system on

          OP with 17-19 balanced bids 1NT without a ♦/♥ ST. RE, before bidding 3NT has to check.