I configured a Softkey Template for Onhook for DND.
When I walk up to the SCCP/7942 Load 8.3(2S) and press DND I get “???” on the left side of screen (similar to where You Have Voicemail would show)
The Common Phone Profile has Turn Ringer Off and Device Phone I've looked at the settings under DND and played around with no luck. Unity Connection 8.5 is a SIP trunk if that matters…but turning off the ringer via DND should be a phone thing..
Using CallManager 8.0;
http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/8_0_2/ccmfeat/fsdnd.html#wp1079981