Each Unify Phone user must be configured in an OpenScape 4000 system as UFIP SIP device. This client device requires a Unify Phone license but it will not use a Flex license (similar to OSMO). Nevertheless, the desk device of a Unify Phone user requires a Flex license even if the desk phone does not exist physical. The UFIP SIP is an auxiliary device, therefore, direct calls are not possible and its number will not be presented on any phone displays. The Unify Phone clients are reachable over the user’s OpenScape 4000 desk phone number. However the physical desk phone is not mandatory, it can be out of service or unplugged but the Signed–Off stations are not supported as desk phones.

The OpenScape 4000 Assistant will synchronize the user data with the Unify Phone Telephony Connector. Therefore, the Assistant must be able to access the Telephony Connector via the Internet (either directly or via HTTPS proxy). The OpenScape 4000 Assistant will retrieve all Unify Phone users which are configured in Unify Video from the Telephony Connector. When the Assistant finds a matching Unify Phone configuration for a user (based on the email address), it will upload the needed connection data to the Unify Phone Connector.

Unify Phone Web and Mobile clients are connected to OpenScape 4000 via SBC. The cluster mode allows to distribute the UFIP SIP devices over several Gateways (GWY) on SoftGates or STMIX/STMIY. Unify Phone Clients can make direct calls to all other OpenScape 4000 stations, external calls (via trunks) and vice versa. Multiple registrations for the same Unify Phone user are possible. All registered Unify Phone Clients and the desk phones will be alerted for incoming calls simultaneously if the Unify Phone user has configured "Default routing". If a second call is signaled or receives busy, the routing depends on the "Busy settings" of the Unify Phone user.