BridgeHands

 Smith Echo - Used when opponents are playing a Notrump contract, a discard signal indicating attitude of partner's opening lead.  The discard signal is provided by the partner of the leader at the first opportunity, typically after declarer has won the trick.  The play of a low spot card signals a discouragement while a high card provides a positive signal to continue the suit of the opening leader.

	8 7 6 J 10 9 4 2 A K 7 6 3
A x x K 7 6 A J 10 8 3 8 4	Declarer: South  Contract: 1 Notrump	K x x 5 4 3 2 Q 7 6 5 9 5
	Q J 3 2 A Q 8 K 9 Q J 10 2

West leads the DJ, won by South's DK; West is unsure who has the DQ.  South then plays CQ -- East shows approval of West's Diamond lead by discarding the high C9 followed by the low C5 as declarer runs 5 Clubs. 

North eventually leads the HJ, but the finesse fails to West's HK.  West confidently leads a low Diamond, anticipating East's DQ.

Also see Details on signaling and books on Signals