Pulse Server
From Zenitel Wiki
One of the intercom stations in a Pulse system must be set as the Pulse Server. The Pulse Server is acting as a server for the other intercom stations in the system. Any IP Intercom station can be a Pulse Server. There must be only one Pulse Server in the installation.
Note that you get extended functionality when using a Turbine station with firmware 4.2 or higher as Pulse Server.
The Pulse Server must have a static IP address (not dynamically assigned via DHCP).