Contacts
Via the soft keyContactto display saved subscriber numbers with names.
If a subscriber number associated with a contact is transmitted during a call, the assigned name will be displayed (instead of the subscriber number). In addition, an individual ring tone can be assigned to the contact.
*Further help under Sound
Additional subscriber number can be saved for each contact.
In addition, the internal subscriber numbers (subscribers, groups, emergency call) are displayed.
All contacts are displayed in alphabetical order in the contact list.
Contacts to whom calls are made frequently can also be displayed in the Favorites list.
Contacts can be saved using backup.
*Further help under Backup and restore
LDAP 
Using LDAP (Lightweight Directory Access Protocol), you can, for example, make phone books on a PBX available to the phone. Stored contact information is called and displayed in
All call lists
contact lists
calls
suggestions lists in dial preparation.
None of the information for a contact is stored on the device.
Requirement for configuration
An LDAP server (for example, a PBX) and a minimum of one configured LDAP account.
Google 
The phone allows synchronisation with the contact data of a Google account.
Requirement for configuration
At least one Google account set up.
Configuration
*Note: The following restrictions apply when setting up:
Only in the phone and via provisioning: create/edit contacts.
Only in the web interface: manage Google accounts and unrestricted LDAP settings
*Note: Only experts should make the settings for LDAP filter. LDAP filter syntax is used. RFC 2254 and RFC 4515 are used.
Web interface: 
LDAP/Google
*Details about the settings are in LDAP/Google
Phone: 
Contacts
*Details about the settings are in Contacts
Settings > Contacts/LDAP
*Details about the settings are in Contacts/LDAP
Provisioning: 
*Details about provisioning this function in the Auerswald DokuWiki at Contacts and Contacts/LDAP