Howard,
I will see if I can help. First of all, I have no experience actually connecting a sla to the STS. The STS comes with two modular plugs on the side of the KSU for providing two single line analog ports, stations 148 & 149. Single line cards can be added to provide 4 analog stations per card. I remember reading in some of the initial STS information about using a stand alone sla, but I have never used one. If you are using a stand alone, it must work OK if you can dial on the intercom. So, I must assume that your problem with accessing outside lines is in programming. I have no knowledge of your programming experience, but let's see if you can follow.
As far as programming goes, let me explain. In order to enable dial 9 access to outside lines, they must be in line group #1. If the outside lines are in a group other than #1, the dial code to access them would be 80X where X is the line group the line is in. Assuming your lines are in the default group of 1, you should be able to access the lines, unless you have for example 3 lines and all 4 line ports are in the default line group 1. Then what happens is that you dial 9 and the system tries to put yo on port 04 which may not be an active line. So, you need to put all unused CO lines in a group other than 1, for example maybe 2, 3 or 4.
So, tell me a couple of more things, and I can reply with the exact programming steps that you should be able to follow.
1. How many incoming lines do you have in the system?
2. What cards are in the system?
3. What station did you assign to the sla adapter?
let me know.
Gary