Handset Abilities

Fields	Explanation
Music On Hold	Controls which music on hold Playlist is used when this handset is used to place a caller on hold.
Call Limit	Limits the no. of concurrent calls that can be set to this handset. The default value of 30,000 is used to effectively remove the limit. Setting a call limit is not normally a requirement. In some cases you may want to set the call limit to 1 so that any subsequent calls are immediately sent to your voicemail rather than waiting for you to complete the active call.
Can Re-Invite	This is a highly advanded feature. It allows a handset to by-pass the PBX and setup a voice channel directly between the two handsets. This can be useful for cloud based systems in that when making internal calls it will reduce the internet bandwidth consumation (as the phones will talk directly over your office network). The disadvanted of this method is that you can no longer record calls.
Can Call Forward	This is a server side setting. Most phones handle call forwarding themselves and as such this setting has no affect in these cases.
Set Variable	This is a highly advanded feature. It allows you to set a channel variable for all calls from this handset. The format of the field is key=value. You are unlikely to find a use for this feature :D