One edit to my above post because this can be really confusing....
when I said:
Again, button 13 of the key module in KEPRO must be function LINE for that to work.
that was the point of confusion.
When you use KEPRO to set up the button table the buttons are numbered 1 - 16 beginning top left and down and finishing top right and down.
When you use KASU or KCSU ro access one of the buttons on the key module they begin AFTER the highest programmable button number on the phone. In the case of my example above, the AdvancePlus has 12 buttons that can be programmed, so the first button on the first key module is referred to as 13 in the programming....
This may confuse the hell out of you, so let me try this as an add-on....
You have 3 sets of christmas lights. The first string has 12 lights, and the next 2 have 25. You plug one of the strings of 25 into the end of the first string of 12 lights. Now even though the first lamp on the string of 25 would be considered lamp #1 of that SET, it is also considered the 13th lamp in the WHOLE STRING.
OK, done with it... I did the best I could

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