SIP and H.323 endpoints and Lync / Skype for Business clients that dial into PIN-protected conferences can bypass the PIN entry screen by including the PIN in the dialed alias.
They can do this by including the relevant PIN (either the Host PIN or the Guest PIN as appropriate) in their dial string when dialing the Virtual Meeting Room or Virtual Auditorium. The dial string should be in the format: **@dial.vc.
For example, if the alias of the Virtual Meeting Room is firstname.lastname@example.org and the PIN is 1234, then the endpoint can dial email@example.com to go straight into the VMR.
Note that H.323 devices can also use the dial format #@dial.vc