32318ae4_tworking___Firewalls_Tutorials_able_4_Network_Devices_Summary_Function_Purpose
[Device] ISDN terminal adapter [Key Points] ISDN is a digital WAN technology often used in place of slower modem links. ISDN terminal adapters are required to reformat the data format for transmission on ISDN links. [Function/Purpose] 
Connects devices to ISDN lines.
Networking - Firewalls Tutorials
Function/Purpose