As devices have become ever more powerful, the function of the address book in your telephone has evolved tremendously. The address book allows you to choose the desired call participants simply by selecting their address book entry, without entering their telephone number. To begin with, the address book was a simple speed-dial memory, in which the telephone number of the party could be assigned to a specific key. With the progress of technology address book functions and data storage options grew considerably. Modern landline, or DECT phones, often offer address books with several hundred entries available. In addition to the name and the landline telephone number further information, such as other telephone and mobile numbers, can be stored. With smartphones and Computer Telephony Integration (CTI) the address book is likened to database, with almost unlimited data storage capabilities for each individual contact.