i'm having trouble with a 616s on a system the phone checks out ok but when pluged in to it normal extention it doesn't work properly, i've changed the extention wire and the patch cable i have a feeling it's in the system programming but do not have a manual. can any one help me out. i can't see paying for a manual for a system that is 20 years old. i tend to think the system is set for a diffrent style phone on that extention.

any help is appreciated