"Introduction Data broadcasting systems utilizing television networks are already implemented in different countries for providing a multitude of services. The quality of these services depends on: ?? the characteristics of the data transmission channel; ?? the effect of these characteristics on the intended services. To provide a suitable service@ measurements on data transmission channels are necessary and appropriate methods have to be devised. Part I of this Report deals with the measurement of the quality of broadcast digital data channels@ Part II discusses the effects of the transmission channel on the service quality in the case of teletext*. * The terms ""teletext"" and ""broadcast videography"" are@ at present@ used interchangeably (see Appendix"" to Recommendation 662)."