PSTN doubt This topic has 2 replies, 1 voice, and was last updated 20 years, 4 months ago by Arijit. Viewing 3 posts - 1 through 3 (of 3 total) Author Posts 19th September 2002 at 16:00 #22092 ArijitGuest Hi, We have 1 pair of wire in local loop but we use 2 pairs for CO to CO connection. Why? Can anyone come out with very good reasoning . I will b greatly helped!!!!!!! Thanks in advance. Arijit 19th September 2002 at 19:40 #22093 RommelGuest Analog carrier vs digital carrier. 2 wire = pots 4 wire = T1 20th September 2002 at 07:08 #22094 ArijitGuest Hi Rommel, Thanks for ur reply. But unfortunately my doubt is why we use 4 lines instead of 2 lines in T1? What problem we may face if it is 2 line in t1 also? Author Posts Viewing 3 posts - 1 through 3 (of 3 total) The forum ‘Voice over IP’ is closed to new topics and replies.