The continuous advance in the development of information and communications technologies, spearheaded by the telecommunications sector, involves a substantial change in our society. Indeed, our society is affected by a continuous increase of new services, resulting in an improvement of the quality of life, as well as of life expectancy. In this context, Common Telecommunication Infrastructures (CTI) play a fundamental role as they structure and guarantee access to these services from the homes. This book presents the Spanish regulations defining the characteristics that these infrastructures must comply with, as well as the structure and contents that the CTI technical projects must present. This book is mainly aimed at students in the compulsory graduate course "Telecommunication Infrastructures" included in the Master in Telecommunication Engineering taught at the Universidad de Jaén, Linares School of Engineering.