Because Microsoft Lync Server 2013 uses non standard SIP protocol for communication, you can not connect 2N® Helios IP as a standard extension, but you must connect it as IP/PSTN gateway. By this way you will be able to receive calls from 2N® Helios IP on your internal extensions. Because trunks in Microsoft Lync Server 2013 do not support video codecs, you will be able to make only audio calls!
Microsoft Lync Server 2013 setting
For creating new IP/PSTN gateway run Lync Server Topology Builder program.
When it is opened, move to Lync Server -> TestLync -> Shared Components -> PSTN gateways folder. Here create new IP/PSTN gateway.
In opened window specify IP address of your 2N® Helios IP and click Next.
If you use IPv6 in your network, you can specify it in the next step. If not then keep the parameters the way they are and move forward.
As a last step define trunk name, port on which is the 2N® Helios IP listening (5060) and port on which is Microsoft Lync listening (ex. 5068). Do not forget to change parameter SIP Transport Protocol to "TCP"!
After pressing Finish button will be the trunk created and you should see it in Trunks folder.
To activate all changes go to main menu and in Action -> Topology choose option Publish....
When the publishing is done, you should see Success for all steps. If any of those steps Fail, then try to create trunk again.
Now you can close Lync Server Topology Builder and open Lync Server Control Panel.
Here in Topology tab you should see newly created trunk to 2N® Helios IP.
2N® Helios IP setting
For proper communication between Microsoft Lync Server 2013 and 2N® Helios IP, you must change transport protocol from UDP to TCP.
You can do this in Advanced setting -> SIP Setting where you change parameter Protocol to "TCP". In this section you can also specify port on which does 2N® Helios IP listen.
Now you can go to Basic Settings -> Phone book and specify here phone number of user which you want to call. Because 2N® Helios IP is not registered to any sip proxy, you must specify number in format for direct call (sip:number@lyncIP: port).
Finally all is set and then if you press quick dial button on 2N® Helios IP, you should see incoming call on you Lync client.