An access terminal box (ATB) is a device that is used in telecommunication networks to terminate and distribute subscriber lines. The functions of an ATB include:

Terminating subscriber lines: An ATB is used to connect subscriber lines to the main distribution frame (MDF) or intermediate distribution frame (IDF) of a telecommunications network. It provides a physical interface for connecting subscriber lines to the network.

Protecting subscriber lines: An ATB protects subscriber lines from over-voltage, over-current, and other types of electrical interference that can damage the lines or equipment connected to them.

Distribution: An ATB distributes the signals received from the main distribution frame to the subscriber lines and vice versa. It allows the signals to be transmitted from the network to the subscriber and from the subscriber to the network.

Testing and maintenance: An ATB provides a convenient location for testing and maintenance of subscriber lines. Technicians can easily access the subscriber lines at the ATB to diagnose and repair faults.

Cable management: An ATB is designed to organize and manage the cables that are connected to it. It provides a neat and organized way to route and secure the cables, which reduces the risk of damage and improves network reliability.