a txnu is a circuit ID for an unbundeled loop (pots line), it is provided from the lec to the clecs for non resold ckt's (meaning the clec has their own switch), for example if an enduser has att local pots service (non unep--resold)but the lec is say sbc. att cannot report a telephone number to the lec but must use the txnu info (as well as co handeoff inforamtion). for the most part the enduser or vendor should never need this informaton, it is more for the service proiveder. now for isdn or high cap service your t1 ckt id is the best way to report trouble to the local carrier,if you are lucky the smart jack or channel bank on site SHOULD (key word here) be labeled especially with all the automated systems local carriers are using they may accept a telephone number for a high cap ckt and route it to the wrong work center, this wil delay repair by a few hours.
