The Jacoby transfer, in the card game contract bridge, is used by a responder following partner's notrump opening bid. For instance, 2 diamond and 2 heart responses following partner's 1 NT opener are conventional bids, each requiring the opener to bid the next higher ranking suit. The one who initiates the transfer promises five-cards in the major suit into which opener is required to bid. The objective is to have the strong hand become declarer whenever the final contract is the major suit.
American bridge players became aware of transfer bids by way of an article in The Bridge World in 1956 by Oswald Jacoby . Transfers have such utility in notrump bidding that they enjoy broad acceptance of most players, in duplicate and in rubber bridge.
Partner opens 1NT. You have a five-card heart suit that may make a better contract than notrump if partner has three or four hearts. Absent the transfer, you would respond in hearts, becoming declarer whenever partner supports hearts. At times it may be more profitable for the strong, opening hand to become declarer because this keeps his honors hidden from the defense; and it results in the opening lead coming into the strong hand.
The transfer procedure is quite simple. Any time you respond to 1NT with a 2 diamond or 2 heart bid, opening partner is compelled to bid the next higher ranking suit. For instance, if you have five hearts and desire to transfer, answer 1NT with 2 diamonds; partner must then call 2 hearts. If your strong partner likes hearts (three-card support) you are likely to play in hearts with partner becoming declarer. Similarly if your suit is spades, bid 2 hearts, forcing partner to be first to call the spade suit. The transfer can be used after 1NT and 2NT openings and certain other situations where partner's last bid was notrump.
When you play the transfer convention, you give up natural diamond and heart responses to notrump openers.
References
Standard applications of the Jacoby Transfer are fully presented in Standard American 21 by John Sheridan Thomas (ISBN 1412020638).
