I would agree with phonemeister make sure your systems are programmed the same for Tie Wink, I would also be careful not to focus completely on the 280, when you activate a T-1 line via the Tie Trunks on the 424 you are actually getting dial tone from the 280 and completing a call; it is the reverse you are having the problem with. Since you have access to Toshibas tech support I will give you a tip we have found effective, we never tell them wheter it is a 280 or 424 rather we focus on the software level of the system ie: a 280 cabinet with 4.3 software is a 424 system Good luck