The defense use signals (when following the suit led) and discards (when discarding a suit other than that led) to provide their partners with information about their hand. This information can suggest what their partner should lead, or provide information about the shape of their hand.

Attitude SignalThis shows the attitude of the signaler towards the suit led. The commonest method is to use the High-Low Signal. Basic SignalThe commonest signal used is to follow suit with a conspicuously high card to encourage the continuation of a suit, and to play a conspicuously low card to discourage.. Count SignalAlso known as Length Signals. The basic principle is to play high then low with an even number of cards in the suit. The lowest card is played when starting wth an odd number of cards. Encrypted SignalThese signals covertly pass information about the bidders hand. They are banned by many international bodies, including the ACBL. Foster EchoThis signal is employed as an unblocking manouever when defending against a NT contract. With a four card suit the second highest card is discarded followed by the third highest. With a three card suid the second highest is discarded followed by the highest. High-Low SignalAlso known simply as an echo. The British also know it as a peter. principle discarding high and then low in a suit shows a preference for the suit to be led again. Odd-Even Discards and SignalsAlso known as Roman Discards and Signals. Playing an odd card signifies encouragement in the led; playing an even card discourages: a low even card suggests the lower of the other two suits (i.e. not the suit led or trumps) and a high even card suggests the higher of the other two suits. Reverse CountThis is a Swedish variation of the High-Low Signal. Playing a low card in a suit by a higher card indicates a even holding in the suit; playing high then low indicates an holding. It avoids the disadvantage of initially throwing away a high card when holding a doubleton. Revolving DiscardThis discarding method provides a suit preference signal on the first discard in a hand. There are two variations: 1) a low card requests the suit below the discarded suit and a high card requests the suit above; 2) a low card requests the lower of the other two suits; a high card requests the higher. Scanian SignalThis is a combination of the standard Signals and Upside-Down Signals. Use normal signals unless a) dummy as a finessable suit, or b) declarer is known to be short or signaler is known to be long. SmithThis signal is employed on the first trick in the defence of an NT contract. Leader’s partner plays low then they are requesting a different suit to be led on the next oportunity; a high card encourages suit continuation. Suit Preference SignalAlso known as McKenney, or Lenventhal. When employing this signal defender follows suit with a conspicuously high card to suggest the lead of the higher ranking of the two other suits (i.e. not the suit led, nor trumps); defender plays a low card to suggest the lower ranking of the two other suits. Trump SignalThis play provides information about the defenders trump holding. When playing trumps, the play of an intermediate card followed by a low card implies that a third trump is held. Upside-Down SignalThis signal is the reverse the the Basic Signal: a conspicuously low card encourages the continuation of the suit led by partner, and a conspicuously high card discourages. Vinje SignalThis is a complex signalling method to pinpoint many distributions and circumstances that are ambiguous when employing other signalling methods.