A network interface device is a device that serves as a demarcation point between the carrier’s local loop and the customer’s on-premises wiring. This is where the data wires end and a customer’s home wiring starts. Phone companies are responsible for maintaining the wiring up to the network interface device, while customers are responsible for the wiring after this point. These devices are located outside of buildings generally somewhere near the utility entrance point.
A network interface device is also known as an NID.
