The board of directors at Thermo Electron Corp. of Waltham, Mass., has approved a one-year plan that will split the company into three independent public entities. The plan includes a divestiture of businesses with aggregate revenues of $1.2 billion. Spectra-Physics Lasers Inc. of Mountain View, Calif., in which Thermo Electron acquired a controlling stake in February 1999, will remain a public company under evaluation. Thermo Fibertek Inc. and a new medical products business will be spun off as dividends to Thermo Electron's shareholders. Thermo Electron will focus on its measurement and detection instruments business; its current design and distribution companies will be integrated into the "new" Thermo Electron. Thermo Electron expects to sell Thermo Cardiosystems Inc., Trex Medical Corp., Peter Brotherhood, Thermo Coleman Corp., Peek Traffic, NuTemp Inc., Thermo Trilogy and the Thermo TerraTech Inc. family of businesses.