[1] 590/3

[2] As regardless one has fulfilled his obligation with this Tekiah blown, as it is considered part of whichever set is the correct set. [ibid] In other words if one has in mind that the Tekiah belongs to whichever grouping is the correct Teruah sound [i.e. one has in mind: “If the תשר“ת is the correct grouping then this Tekiah is the last Tekiah of the grouping, and if the תש“ת is the correct grouping then this Tekiah is the first Tekiah of that grouping”], then the Tekiah is valid for either set and one does not need to blow another Tekiah before beginning the Shevarim of תש“ת.

The reason why a stipulation is necessary: If one does not make a stipulation on the Tekiah then the Tekiah cannot serve for both sets of blows, such as for both Tashrat and Tashat or both Tashat and Tarat. The reason for this is because Mitzvos need intent and when one blew the last Tekiah for the set of Tashrat he intended it to count for that set and thus it cannot count for the set of Tashat as if the main set is really Tashat then it ends up that this first Tekiah which was blown for the sake of Tashrat was not blown for the sake of the Mitzvah at all. The same applies by the last Tekiah between Tashat and Tarat. Hence if one did not make a stipulation he is required to repeat a Tekiah before each set. [ibid]

[3] One intends: “If  תש“ת is the correct grouping then this Tekiah is the last Tekiah of this grouping, and if the תר“ת is the correct grouping then this Tekiah is the first Tekiah of this grouping”

[4] In total one saves two Tekias from being blown. In a case that one is blowing many times consecutively, such as on Mivtzaim, it is advisable to intend this stipulation in order to conserve ones strength to blow for other people.