The Truscott convention is played after the opponents have done a take out double, which occur rather frequently. In MAF, as in some other systems as well, the application is restricted to major suit openings of your partnership.

If you as the responder have a fit in the opening suit "", you add 3 points to the total value of your hand. Now you call your partners suit on this new base. When this results to a bid of 3 or higher, you call 2NT instead to show you are strong.
So, the direct answers of 2, and 3 both are preemptive. If you use the "by pass" and call 2NT first and later on a new suit, this is a control bid, showing that you have overvalue and that the contract must be at least 3.

After reponder's 2NT bid the opener calls the lowest suit that he controls (A, K, void or singleton); he never exceeds 3 without having overvalue, in which case, and still without controls in the minors, he may call 4. He is also allowed to do this on his next turn, in case the responders walks out to 3.

In fact the opponent's "double" has made the "2NT response" a multi-way bid: it may be "a real limit raise " and it may be also the "strong conventional " Jacoby-2NT

Any call after the double in a new suit has the same meaning as if no double had been done at all. The diagram counts commonly.

The Truscott convention is primarily aimed to annoy the opponents, by making it hard for them to find a fitting suit. Therefore it is wise to bid preemptive as soon as you discover a fit. Only if the responder is strong you can afford to stay low, because the 3-level will be reached anyway.
The responses redouble and 1NT - major suit Sohl are done only (if they ever are done at all) with strong hands (long trump suit or >=10 hcp's). Holding a 2-card support and 8-9 hcp's, 3©/ is bid, the support is to weak for the Sohl, which commonly should have been applied without the double.

If you want to see examples of bridgames in which the matter, treated above, is practiced you should click on examples and choose for the appropriate convention or for any other typical call.