Won’t you call my private number?

...we can go away for the summer.
We can drive around with the top down.
Stereo turned up loud with a fat sound. :-)

With Lync it is possible to configure a private number - an additional telephone number which you can hand out to your closest friends. A call to a private number will bypass call forwarding (i.e. not be forwarded), and "Do not disturb" status. If the receiving user have configured simultaneous calling the secondary number will ring, probably because of Lync assuming that the secondary number belongs to the receiving user. It is not possible to set a status such as "Do not disturb" on the private line, it is always "open". It is possible to select a different ringtone for calls coming in on the private line, this is done in Tools / Options / Ringtones and Sounds in the client. A call to a private number will also generate an additional line in the call toast stating "Private Call" as seen in the picture. 

Some limitations of the private line is that it will work only for inbound calls, a user cannot use the private line to make an outbound call.  Voicemails recorded on the private line will be sent to the same Exchange UM mailbox as the users LineURI. Private telephone lines are available in Lync on-premise only, not in Lync with Office 365, also mixed environments with Lync and OCS 2007 will not work to a 100%.

Unfortunately there is no way of seeing a private number in the Lync Control Panel so Powershell must be used:

Get-CsUser mk@kressmark.com | Format-Table -Property DisplayName, LineURI, PrivateLine -AutoSize

DisplayName       LineURI          PrivateLine
-----------       -------          -----------
Mattias Kressmark tel:+46736405540 tel:+46736405541

This will show if a user has a private number configured or not.
To set a private number use the following command:

Set-CsUser mk@kressmark.com  –PrivateLine “tel:+46736405541”

From the Lync documentation:

Private Telephone Lines

Get-CsUser

Set-CsUser