The Dynalink ISDN Adapter (PCI Bus D C) is a type of ISDN (Integrated Services Digital Network) adapter manufactured by Dynalink, a company known for producing various communication hardware like modems and network cards. An ISDN adapter enables a computer to connect to an ISDN network for digital communication, including high-speed data transfer, voice, and fax services. The "PCI Bus D C" part of the description refers to the fact that the ISDN adapter is installed on your computer's motherboard via a PCI (Peripheral Component Interconnect) bus.

The Windows driver is necessary to allow Windows to communicate with and configure the ISDN adapter. The driver enables the device to work with various software applications, manage ISDN connections, and support network configurations.