Signals And Discards

Board 1
North Deals
None Vul
Q J 7
9 3
Q J 9 8 4
J 10 9
K 5 4 3
Q J 10 7
5 3
7 4 2
N
WE
S
A 10 9 6 2
8 5 4
A K
K Q 6
8
A K 6 2
10 7 6 2
A 8 5 3

WestNorthEastSouth
 Pass1Dbl
2Pass3All pass

3 by East

Lead: A

On the A lead, North must encourage with 3 (low = like).
South can show which suit to return by playing a low heart on the 3rd round.
(low = lower side-suit = suit).
South then wins A and returns another heart to be ruffed by North to prevent a club discard.