cases this capability can also be implemented in the device drivers of passive ISDN adapters. active Active ISDN adapters are top-of-the-line ISDN cards, and the most expensive.
—Active ISDN adapters handle all ISDN protocols on OSI Layers 1, 2 and 3. These cards have one or more on-board microprocessors and a certain amount of RAM. Active ISDN adapters relieve the host system's CPU of all ISDN communication processing. Their primary area of application is in RAS servers, for which many manufacturers offer a special line of active adapters.
Note: ISDN adapters cover OSI Layer 1, but differ in the higher-layer protocols that they provide!
•AO/DI - Always On/Dynamic ISDN. This is an ISDN technology that was originally developed by IBM and is now an open ISDN standard. This technology is currently only used in the United States of America and Canada. AO/DI allows the user to connect to an ISP (Internet Service Provider) for example, then drop the idle B-channel connection after a delay. A D-channel connection is maintained, however, and permits a quicker reconnection when data is queued.
•B channel - One of the two channel types available in ISDN. The B channel is primarily used for data transfer at 64 kbit/s in each direction.
•Basic-rate interface - One of the two channel types available in ISDN. The B channel is primarily used for data transfer at 64 kbit/s in each direction.
•BRI - See basic-rate interface.
•CAPI - Common ISDN API. This is a programming interface for ISDN that has been developed in Germany and is today a de facto standard for European ISDN cards. CAPI allows software developers to write ISDN- capable applications without having to deal with specific ISDN adapter implementations– as long as the adapter is equipped with CAPI device drivers. Thus any CAPI-compliant application software works out of the box on any CAPI-compliant ISDN device. The CAPI interface is independent both from the telephone company's implementation of ISDN and from the hardware manufacturer's implementation of the ISDN adapter. CAPI is thus universal. The CAPI interface has been defined for a broad range of operating systems, including DOS, Windows 3.x, Windows 95, Windows NT, Linux, etc. More information can be obtained from http://www.capi.org.
—CAPI 1.1 was the original CAPI specification for the German ISDN implementation.
—CAPI 2.0 is the current CAPI specification for Euro-ISDN.
The IBM International ISDN PC Card is fully CAPI 2.0-compliant.
•cFos - CAPI Fossil device driver. This device driver package emulates an analog modem over a CAPI-compliant ISDN adapter. Many communications applications today still expect to talk to an analog modem through a COM port. cFos gives such software the impression of talking to an analog modem, even though the underlying hardware is in fact an ISDN adapter. cFos only works with CAPI-compliant devices such as the IBM International ISDN PC Card.
224IBM ISDN PC Card:User’s Guide
