Hi, I have a TC1000 with 3 E1 Hiper DSP card and 4 analog card, sometimes users who want to connect to E1 lines; receive busy tone or silence . only when we plug out and plug in E1 card, they can connect to it. it is not on a specific card and all 3 cards have this problem. How do you think about this problem? We have changed 130 Am Power also Hiper ARC and NMC card. still the same problem. Do you think it is for a problem with chassis? Best Regards Shahrooz Sharghi