Hi Nicholas,

Sadly this feature is only available CCM 4.2 and CCM 6.0 with the Login/Logout of Hunt Groups feature. CCM 5.x came out early to address the market needs for SIP and perhaps the Linux Appliance model. CCM 5.x is actually based on CCM 4.1.3 whereas CCM 6.x is based on CCM 4.2.x Have a look;

Log Out of Hunt Groups

The Log Out of Hunt Groups feature allows phone users to log their phones out from receiving calls that get routed to directory numbers that belong to line groups to which the phone lines are associated. Regardless of the phone status, the phone rings normally for incoming calls that are not calls to the line group(s) that are associated with the phone. The phone provides a visual status of the login state, so the user can determine by looking at the phone whether they are logged in to their line group(s).

The Log Out of Hunt Groups feature also comprises the following components:

The HLog softkey allows a phone user to log a phone out of all line groups to which the phone directory numbers belong. Configure the HLog softkey in the Softkey Layout Configuration window. When the user presses the HLog softkey, the phone screen displays "Logged out of Hunt Group." When the user presses the HLog softkey again to log back in and receive hunt group calls, the "Logged out of Hunt Group" notification on the phone screen clears.

The Hunt Group Logoff Notification service parameter in the Clusterwide Parameters (Device - Phone) section of the Service Parameters Configuration window for the Cisco CallManager service must be configured to enable this feature.

The Log Out of Hunt Groups feature, which is device-based, operates differently for non-shared lines and for shared lines.

http://www.cisco.com/en/US/products/sw/voicesw/ps556/prod_release_note09186a00805f1470.html#wp2440103

In the CCM 4.1.x and 5.x trains there is really not an equivilant feature. The best you can do is probably using AC Hunt :(

Hope this helps a little!

Rob