transfer when the bidding begins:
(1N) - X - (P) - ?
assume the overcaller's Double shows around 15-17 points, a common treatment
for partners who play natural overcalls or conventions such as the
Cappelletti (Hamilton) convention.
players choose to play "systems on" when partner shows a strong hand.
As we've all learned in bridge basics, we want the lead coming to the
stronger hand (the Doubler here), which is typically worth at least one-half
of trick. And of course we know it's better to keep the stronger hand
unexposed. Yet some top players do not play systems on in any
competitive auctions, so it's purely a matter of partnership agreement and
after Double of opener's Notrump can also extend to conventions other than
the Jacoby 2 Notrump. Imagine the auction:
(1N) - X - (2H) - ?
Where 1N is a Weak NT
play "all systems on" here, including
Lebensohl, etc. Here's some books