Although Freepbx allow the option, the Nautilus deployment on sip device is on PJSip.
With PJSiP configuration, customer can get devices paired into one extension. In other words, all registered device falls under one extension account.
That way we can better keep a good record of a person and their extensions belonging to them.
Make sure to create a PJsip extension and follow the extension setup procedure in Freepbx. Don't forget to set max concurrent channel to the number of devices registered I the system.
By setting PJSIP, you have many phones but one extension set. That eases administration and customer knowledge transfer