IEC 60747-5 is the part of the discrete semiconductor device series that covers optoelectronic devices. It is a specification standard rather than a test method standard: its purpose is to define the terminology, the letter symbols, the essential ratings and the essential characteristics by which each family of optoelectronic device is described, so that a datasheet from one supplier can be compared with a datasheet from another. The family is broad and includes light-emitting diodes, infrared emitters, photodiodes, phototransistors, optocouplers and optical isolators, together with the associated display devices. For each device type the standard identifies the maximum ratings that must not be exceeded, such as forward current, reverse voltage, power dissipation and junction or storage temperature, and the characteristics that must be stated, such as luminous or radiant intensity, forward voltage, coupling efficiency and switching times. It also prescribes the conditions under which these quantities are measured and the methods for verifying the ratings, including electrical, thermal and endurance tests, so that the published data is reproducible between laboratories.