The document discusses procedures for calibrating a Co60 gamma ray beam using IAEA TRS-398 protocol. It describes the necessary equipment including a water phantom, ionization chamber, electrometer, barometer, thermometer, and connecting cables. The aim is to perform an output calibration of Co60 by determining the absorbed dose under reference conditions defined as a water phantom, cylindrical chamber at a depth of 5g/cm2, field size of 10x10cm2, and other parameters. Equations are provided to calculate absorbed dose to water based on measurement readings and various correction factors for temperature, pressure, polarity, saturation, and beam quality.