How to make a non-busy extension become a key appearance

Mitel documentation will tell you that you cannot have a "Non-Busy Extension" appear as a key line appearance on a Superset.

Actually, you can and the "how-to" is easy.

[Color red]Disclaimer: You're on your own with this. What follows is an unsupported configuration[/color]

1) start by programming an ONS port as a non-busy ext; give it a D-I-D number
2) next create a new analog loop-start 2-wire trunk
3) assign this trunk its own separate trunk service number (mandatory)
4) program an unused DN (recommend non-DID, and preferably something non-guessable) as a single line RING appearance on the superset(s) where you want the NBE to appear, i.e., use a number like 10*0 (one-zero-star-zero)
5) add this "funny number" to your teldir, name it whatever you want and be sure to make it "private" so no one will see the trick number and try to dial it directly
6) assign this new DN to the non-dial-in answer points (day/Night1/Night2) in the Trunk Service Assignment form for your new LS trunk that you created in step 2 above
7) at the MDF bridge the LS trunk directly onto the PLID of your NBE

Done.

Some operational caveats; Beware that an NBE call will not clear-down by itself at the end of the call. This is the nature of the beast. You must physically "hang-up". This holds true whether the answer point is an analog set (ie, Polycom speakerphone) or a Superset, otherwise the line will "lock out" at the end of the call. Make companion "key system" line appearances of this line at your own risk and be sure if you do, to release privacy. Note that this is effectively the same as connecting two internal conference bridges together. Yes, you can build a bigger conference bridge this way (up to 39 parties), but results could be unpredictable. Finally, I don't recommend assigning the non dial-in answer point (the trick number) to the prime line of the instrument. Yes, you can certainly do it, but you may wind up wishing you hadn't. (see step 4 above). We don't want people calling the "secret number" of the LS trunk answer point, we want them calling the DN of the NBE. On the other hand, a good case can also be made for using the prime line. The scenario I'm thinking of here would be a situation where the NBE was initially answered on the prime line of the superset and the superset user wanted to dial-out to add some additional parties that did not call-in to the NBE number. (This would use the ADD HELD feature on the superset, which only works from the prime line).

Programming tip: assign the prime line of the superset to a 6-digit dummy number that has the same last 4 digits as the NBE. That way any outbound calls to the PSTN from the superset will show the caller-ID of the NBE. Example, use something like 004728 as the prime number where "4728" is the DN of the NBE.

Below added for the newbies who have e-mailed me:
D-I-D = Direct Inward Dial
NBE = Non-Busy-Extension
DN = directory number
MDF = main distribution frame (the telephone wire connecting block)
PLID = Physical Location ID (card slot & circuit nbr in the PBX)
ONS = On Premesis Station (analog line)
PSTN = Public-Switched Telephone Network (Ma Bell)