This part of IEC 60794-1 defines test procedures to be used in establishing uniform requirements for the environmental performance of " optical fibre cables for use with telecommunication equipment and devices employing similar techniques, and " cables having a combination of both optical fibres and electrical conductors. Throughout the standard the wording "optical cable" can also include optical fibre units, microduct fibre units, etc. This part defines a test standard to determine the ability of a cable to withstand the effects of freezing water that can immediately surround the optical fibre cable sheath by observing any changes in the physical appearance of the sheath, or in the measured cable optical attenuation. Method F15A is a test standard to simulate freezing of the medium surrounding a buried cable, as in wet earth or water. Method F15A is moved from Method F15 in IEC 60794-1-22, Ed. 2 without any technical changes. Method F15B is a test standard to simulate freezing of the medium surrounding an outside cable in a conduit (duct) which is made of rigid material, e.g. steel. See IEC 60794-1-2 for a reference guide to test methods of all types and for general requirements.