A double dissolution is a procedure permitted under the Australian Constitution to resolve deadlocks in the bicameral Parliament of Australia between the House of Representatives (lower house) and the Senate (upper house). A double dissolution is the only circumstance in which the entire Senate can be dissolved. Similar to the United States Congress, but unlike the British Parliament, Australia's two parliamentary houses generally have almost equal legislative power (the Senate may reject outright but cannot amend appropriation (money) bills, which must originate in the House of Representatives). Governments, which are formed in the House of Representatives, can be frustrated by a Senate determined to reject their legislation. If the conditions (called a trigger) are satisfied, the prime minister can advise the governor-general to dissolve both houses of Parliament and call a full election. If, after the election, the legislation that triggered the double dissolution is still not passed by the two houses, then a joint sitting of the two houses of parliament can be called to vote on the legislation. If the legislation is passed by the joint sitting, it is deemed to have passed both the House of Representatives and the Senate. The 1974 joint sitting remains the only occurrence in federal Australian history. Historically, a double dissolution election has been called in lieu of an early election, with the formal trigger bill not playing a significant role during the subsequent election campaign. There are also similar double dissolution provisions in the South Australian state constitution. Constitutional basis Part of section 57 of the Constitution provides: If the House of Representatives passes any proposed law, and the Senate rejects or fails to pass it, or passes it with amendments to which the House of Representatives will not agree, and if after an interval of three months the House of Representatives, in the same or the next session, again passes the proposed law with or without any amendments which have been made, suggested, or agreed to by the Senate, and the Senate rejects or fails to pass it, or passes it with amendments to which the House of Representatives will not agree, the Governor-General may dissolve the Senate and the House of Representatives simultaneously. But such dissolution shall not take place within six months before the date of the expiry of the House of Representatives by effluxion of time. Section 57 also provides that, following the election, if the Senate