Source: The oddball, or alarm clock
One of the signals that experts use very occasionally is called the oddball, or alarm clock. The idea is that the sacrifice of a high honor is used to wake up partner to the idea of an unusual switch, frequently to obtain a ruff.
In the deal that follows from the 1999 World Junior Championships, East and West managed precisely that feat, in a situation where, in the absence of such methods, the defense would have been almost impossible to find.
Although five diamonds was laydown for East-West, it was very difficult for East to appreciate this after his partner had overcalled in spades — suggesting to him that the partnership assets might be better on defense than offense. Perhaps West has to bid five diamonds at his second turn.
Still, at least one pair managed to find the right defense to their opponents’ heart game. Juan Carlos Castillo and Juanita Ochoa were the pair defending the game.
Opening Lead: 
A
Ochoa followed with the diamond queen under her partner’s lead of the diamond ace against four hearts, denying the king and suggesting that her partner wake up to do something unusual. A discouraging card would have led to the club shift, of course, but Juan Carlos dutifully played a spade for down one.
Well done!