[Flame]

What is the effect of playing support doubles on later doubles.
1d (P) 1M (1S/2)
P (P) D
partner denyed 3 card support, what is responder double now, is it change whater there is an unbid major ?

and now the other side of it
1d (P) 1M (1S/2C)
D (2S/3C) D

This time partner showed exactly 3 card support, is my double t.o or penalty.

There are ressons to play it as penalty oriented since we have a good idea of our fit, but this is not absulute, we can still have a fit in other suits, and especially when there is an unbid major there is a good resson to play the double as t.o.

[FrancesHinden]

Like all of these things, this is now a matter of agreement.

My agreement is that opener's rebid (call) defines her hand, so after a support double all subsequent doubles are penalties. This agreement has one big advantage: we never get it wrong!

For the first auction, I'm not sure it matters so much whether or not you play support doubles, responder's double is still take-out. It has an impact on the subsequent auction, e.g.

1C P 1S 2H
P P x P
2S

is Hx support (or even two low if you are desperate) in a balanced hand.

[Kalvan14]

The first case is certainly t/o.

The second one depends on partnership agreements (and also if you play or not G/B 2N). The problem is when you want to compete, obviously: with G/B 2N, X should propose a penalty). Without it, t/o is more productive.