Hello: First thanks to all users. With your help, I am getting 3COM almost working. Now the next problem: 1 - HiPer NMC 2 - HiPer ARC 10 - HiPer DSP 2 - T1 ISDN PRI 23B + 1D Channels HiPer ARC 1 (Slot 15) controls odd numbered (1,3,5,..) HiPer DSP Slots. HiPer ARC 1 (Slot 15) controls even numbered (2,4,6,..) HiPer DSP Slots. I am testing HiPer DSP located in Slot 1 & Slot 2. First I connected the T1 Line into HiPer DSP on Slot 1. It worked fine. Then I moved the T1 to HiPer DSP in Slot 2 (no T1 in Slot 1). HiPer DSP in Slot 2 also worked fine. Then I connected one T1 in HiPer DSP in Slot 1 and another T1 into HiPer DSP in Slot 2. Now the error: The front panel light 'LPBK/D-ALM' on each HiPer DSP turns GREEN & then RED. Also, when the 'LPBK/D-ALM' light on HiPer DSP in Slot 1 is GREEN, the same light on HiPer DSP in Slot 2 is RED & vice versa. New Users can not connect & the one who are connected are disconnected. What is the problem and how to fix it? Kirti PS: If my explanation is confusing, please let me know. I will try to clarify it.