I have just fitted a second hand one for a company, who supplied it themselves. two analogue lines going in, the problem is: when you use a phone, that line goes red for all other users, as it should, when you put the phone down, the line is cleared, BUT the lights dont go green on the other phones until a minute after and if you ring that line, you get the ringing tone,but no phones ring and because the line appears open, it doesn't get transferred to line 2. so basically if someone has been on lines 1 and 2 , nobody can ring in or out for a minute afterwards. I think its a fault in the black analogue card and am going to recommend them to get another one at £150. anyone fitted similar systems? any other theories.