I look after dozens of E1 lines and hundreds of ISDN2 lines. Quite often when we have faults, I have to teach the BT Openreach engineers how to use the diagnos

I look after dozens of E1 lines and hundreds of ISDN2 lines. Quite often when we have faults, I have to teach the BT Openreach engineers how to use the diagnostic equipment to track down where the fault is.