A hard-copy index of telephone numbers by the names of the subscribers in a POTS, or an electronic edition of similar contents with varying degrees of sophistication.
In NewZealand the TelephoneBook is at 
http://www.whitepages.co.nz and http://www.yellowpages.co.nz. The former lists numbers by name (both residential and business), the latter by category.
One page links to TelephoneBook:
