How do I enable the test line in LD 15 for an 81c? I have one that works in my 61c's, but I can't get it to work in any of my other 81c. I can program the numbers in the t100 and ref0 and so on but all I get is a fast busy when I call them. I see that in the Alphabetical list of prompts page 367 for LD 15 that their is a Prompt "TSL (NO) YES Test lines for this customer", but I can not find where to say yes. Any ideas?