In telecommunications, the term network interface device (NID) is interchangeable with network interface unit (NIU)
Meanings of the term
A network interface, also commonly referred to as a smart jack, is typically in the basement, first floor telco room, garage, or even outside the building. NIUs are multi-functional devices, which include a protector block to prevent high-voltage surges from affecting premise equipment and inside wiring. It also usually allows the carrier to initiate a loop-test back from the central office to test the integrity of the local loop.
- A device that performs interface functions, such as code conversion, protocol conversion, and buffering, required for communications to and from a network.
- A device used primarily within a local area network (LAN) to allow a number of independent devices, with varying protocols, to communicate with each other.
An NID converts each device protocol into a common transmission protocol.
The transmission protocol may be chosen to accommodate directly a number of the devices used within the network without the need for protocol conversion for those devices by the NID.
References
Source: from Federal Standard 1037C