This information is stored in the Base Station. After a few seconds, the handset will retrieve the data from the base. Thereafter, call log or phonebook information will be displayed on the handset when you press either call log or phonebook button (see image below)
Note: With phonebook and call log information stored in the Base Station, users with Duo, Trio or Quattro sets can have access to the same phonebook and call log, no matter which handset they are using. There is no need for synchronization or data transfer.