Using Fusion/Yealink together (some other PBX' not capable), you set the extension to SLA [YES]. Using SLA, you get the old Nortel Meridian similarities, whereas multiple endpoints can be registered with the same extension. All devices using SLA, using the same extensions and passwords will receive the calls. 1st to answer, gets the call. Another major benefit is the HOLD. All extensions "lines" will also HOLD. Its an alternative to the ring group. Some clients, who are accustomed to older phone systems, will prefer this 1 line per call scenario. Old school but its what they are used to. I have been using it without fail on Yealink and Fusion. There are no Fusion configurations required.
For those users who have been using analog for 25+ years.
Downside is CDR's. All calls in and out will only show that extension (SLA) used.