I have a kxt 1232 and need one of three single line ports to go out on a specfic trunk. like a prime line, for a fax. the other two single line phones dial 9 and go out over different trunks.
Is this posable? I tried hooking up a propriatry
phone and set it a prime line but this did not cary over to the single line jack.

You could set that single line extension to "hot line" to the trunk group that you want.

If you want the fax to always grab line 5 for example, and line 5 is in trunk group five, then have that extension hot line to 85 (85 is the code to grab trunk group 5).

Look up hot line in the user manual, there's a code to set it on an extension.