This paper describes a B-ISDN terminal adapter which provides B-ISDN adaptation functions for conventional services such as N-ISDN, video, connectionless data service in the ATM based B-ISDN. These services are provided individually or simultaneously. The B-ISDN terminal adapter offers interfaces of N-ISDN, video codec, Ethernet for supporting conventional services. And it provides various types of services which are available in conventional terminals and networks through B-ISDN. The AAL type 1 is used for N-ISDN and video services, the AAL type 3/4 and 5 are used for LAN service.