Exhibit 4.3 FIRST SUPPLEMENTAL INDENTURE FIRST SUPPLEMENTAL INDENTURE (this "First Supplemental Indenture") dated as of February 6, 1998, by and among ThermoTrex Corporation, a Delaware corporation (the "Issuer"), Thermo Electron Corporation, a...First Supplemental Indenture • May 14th, 1998 • Thermotrex Corp • X-ray apparatus & tubes & related irradiation apparatus
