Compilation of works resulting from years of lectures in the field of telecommunications, information technology, information protection and digital forensics is an attempt to create a general picture of the listed areas. The same can be used as a teaching curriculum for more subjects, such as teaching staff, but also those who are in love with these areas, who, besides the scientific background, are interested in the basics of functioning of the telecommunication channel for general purposes, without the protection of information, for special purposes, with the protection of information.