The Standing Rules of the Senate are the parliamentary procedures adopted by the United States Senate that govern its procedure. The Senate's power to establish rules derives from Article One, Section5 of the United States Constitution: "Each House may determine the rules of its proceedings..." There are currently forty-five rules, with the latest revision adopted on January 24, 2013. The most recent addition of a new rule occurred in 2006, when The Legislative Transparency and Accountability Act of 2006 introduced a 44th rule on earmarks. The stricter rules are often waived by unanimous consent. Outline of rules Quorum The Constitution provides that a majority of the Senate constitutes a quorum to do business. Under the rules and customs of the Senate, a quorum is always assumed to be present unless a quorum call explicitly demonstrates otherwise. Any senator may request a quorum call by "suggesting the absence of a quorum"; a clerk then calls the roll of the Senate and notes which members are present. In practice, senators almost always request quorum calls not to establish the presence of a quorum, but to temporarily delay proceedings without having to adjourn the session. Such a delay may serve one of many purposes; often, it allows Senate leaders to negotiate compromises off the floor or to allow senators time to come to the Senate floor to make speeches without having to constantly be present in the chamber while waiting for the opportunity. Once the need for a delay has ended, any senator may request unanimous consent to rescind the quorum call. Debate The Senate is presided over by the Presiding Officer, either the President of the Senate (the Vice President) or more often the President pro tempore (in special cases the Chief Justice presides). During debates, senators may speak only if called upon by the Presiding Officer. The Presiding Officer is, however, required to recognize the first senator who rises to speak. Thus, the Presiding Officer has little control over the course of debate. Customarily, the majority leader and minority leader are accorded priority during debates, even if another senator rises first. All speeches must be addressed to the Presiding Officer, using the words "Mr. President" or "Madam President". Only the Presiding Officer may be directly addressed in speeches; other members must be referred to in the third person. In most cases, senators refer to each other not by name, but by