Question

U interface in ISDN is the interface between
1. PSTN and Desktop
2. TA and ISDN Phone
3. TA and non-ISDN Device
4. TA and PSTN

Answer 1

Correct Answer - Option 4 : TA and PSTN

The U interface or U reference point is a Basic Rate Interface (BRI) in the local loop of an Integrated Services Digital Network (ISDN). It is characterized by the use of a 2-wire transmission system that connects the network termination type 1 (NT1) on the customer's premises and the line termination (LT) in the carrier's local exchange.