The ninth Plenipotentiary Conference of the International Telecommunication Union (ITU) took place in Montreux, Switzerland, between September 14 and November 12, 1965, under the chairmanship of Gustav-Adolf Wettstein (Switzerland). The main task of the Conference was the revision of the previous Convention, drawn up by the preceding Plenipotentiary Conference in Geneva in 1959. The new Convention was to enter into force on January 1, 1967. In one of its major decisions the Conference agreed in principle on a Constitutional Charter eventually to replace the Convention, and it instructed the Administrative Council to set up a study group to prepare the draft of such a charter in sufficient time for it to be distributed at least one year prior to the next Conference, scheduled to be held in 1971. The Conference approved the Union's accounts for the years 1959–1964 and fixed the limits of expenditure for the period 1966–1971, providing for slight annual increases in this expenditure. It also approved the purchase of the new headquarters building by December 31, 1965.