Wis. Stat. § 756.05: Jury summons, when and how issued.

At least 12 days before the first day on which a jury is required to be present, to create the jury venire, the clerk of circuit court shall randomly select a sufficient number of prospective jurors from the jury array created under s. 756.04 (9) who shall be summoned to appear before the court at an appropriate time for jury service. The summons may be served by 1st class mail or another method.