[ICOM] IC-3AT tone board question

[Tom WA9WSJ]

Hello Gents,
I acquired an IC-3AT, 220 hand held. It works! But there is no tone board. 
The manual that I found mentions a 'spare switch' on its top, suggested tone switch in the manual, but it is not wired to anything, I checked.
Has anyone ever successfully incorporated a tone board into it? 
One of our local repeaters does not require a tone but another does.
Thanks!
73Tom wa9wsj