In Unity 4.0(5), Unity 4.1 and Unity Connection 1.1 there are a couple limitations involved when using two digit menu entries that you should be aware of.  

 

The primary issue to be aware of is if you have a two digit sequence, say "18" mapped to a menu entry and you do not have a "1" key mapped to any option in that menu, users may experience some unexepcted behavior if they press 1 and nothing else at that menu.  Instead of hearing "invalid selection, please try again" as normal, this is treated as a timeout and in most cases the conversation will exit out of the current menu and go back up a level as if the user pressed nothing and the menu repeated the maximum number of times and timed out.  

 

If you have the same configuration as above and the user presses "1", Unity must wait for the interdigit timeout to see if the caller will press "8" or not.  This is not a bug but you should keep it in mind when deciding on your key layout.  Keys that have no other possible keys after them will trigger immediately.

 

As noted elsewhere, the message header/body/footer have some hard coded behavior for the jump ahead/back, volume up/down, speed up/down and pause keys - these cannot be mapped to two digit key sequences at this time.  The Custom Key Map utility will not allow you to assign two key entries for these items so you don't need to worry about accidentally doing this.

 

Note: For Unity 4.2(1) and later you can use 3 digit sequences for all functions other than the pause function during message playback which is limited to 1 digit.  For versions of Unity earlier than 4.2(1) you are limited to 2 digit sequences.