This International Standard specifies the principles of transmission techniques. Transmission techniques can be used for: — detection of imperfections; — determination of attenuation. The general principles required for the use of ultrasonic examination of industrial products are described in ISO 16810. The transmission technique is used for examination of flat products, e.g. plates and sheets. Further, it is used for examinations e.g.: — where the shape, dimensions or orientation of possible imperfections are unfavourable for direct reflection; — in materials with high attenuation; — in thin products.