Sometimes the box that creates the demarcation point in the network is in fact a specialized and intelligent device. They are usually referred to as smart jacks (see Figure 20.3 below) but they are also called:
- Network interface devices (NIDs)
- Network interface units
- Telephone network interfaces
Figure 20.3 – Smart Jacks
The smart jack is more than just a simple interface. It can be in the form of a circuit card in a chassis and it is often useful for the WAN or ISP so it can check the status of the connection. The service provider can run remote diagnostics and tests on the WAN connection by sending signals to the smart jack to detect any problems with sending traffic from their side to the customer side.
Smart jacks also include alarm indicators and sensors so the service provider can remotely check the status of the demarcation point.