Signals are among the most valuable tools the defenders can employ to help them overcome the natural handicap of defense. In general, these signals take two forms — they are either positive or negative.

A positive signal when you are discarding or following to partner’s lead is the play of a card higher than necessary. Thus, if your partner leads the king of a suit and you hold, say, the A-8-2, the play of the eight is a positive signal asking your partner to continue the suit. If you were to play the deuce instead — a negative signal — you’d be asking partner to stop playing the suit.

Similarly, if you’re out of a suit that’s led, you can signal in another suit by discarding a high card (positive) or a low card (negative) of that suit.

It is vitally important to know how to send and receive signals. Good defense depends on it. Today’s hand provides an example of how the process works.

Assume West leads a spade against four hearts. Declarer wins with dummy’s queen, East playing the deuce, and leads the nine of trump to West’s queen. West then cashes the ace of trump, on which East discards the three of clubs.

West thereupon shifts to a low diamond, and when declarer plays the king from dummy, the defenders cash three diamond tricks to put the contract down two. If West had not switched to a diamond at trick four, declarer would have finished with 10 tricks.

West’s diamond shift is based on East’s signals in spades and clubs, East signaled negatively by playing low in each of those suits. In effect East asked his partner to lead the only suit left — diamonds. East’s negative signals thus produced a positive result.

Tomorrow: Bidding quiz.