Have an IP500 with 6 analogue trunks from BT and occasionally some of the lines will lock up, I currently have DCT set to 150ms and I have checked with the supplier and they are currently set to 500ms. According to Avaya documentation the DCT should be at lease 150ms below that of the provider which this is but I still get line lockup, anyone had this before or can suggest an alternative to the 150 ms currently set. The customer is having and ISDN conversion but this wont be for at least a month.