What are terminal adapters and what is an NT1?
An ISDN terminal adapter is similar in function to a telephone modem. Call setup (dialing), rate negotiation, and call termination functions are all performed by the terminal adapter. In addition, the terminal adapter converts the user data into a format required by the network for transmission. The NT1 is an interface converter. The three channels of ISDN are all combined onto a single twisted pair from the service provider. The terminal adapter requires that the three channels be separated into a 4-wire system, and that is the function of the NT1. In North America, the phone company provides a 2-wire ‘U’ interface and an NT1 is required. It is the user’s responsibility to provide the NT1. Elsewhere, the phone company provides the NT1. Some terminal adapters sold in North America integrate the NT1 functions into the terminal adapter, such as our TA301 internal terminal adapter and the ADTRAN 2X64 terminal adapter. How much does ISDN cost? This question is a little hard to answer. The
