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224 IBM ISDN PC Card:User’s Guide
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.
ISDNmst.fm Page 224 Wednesday, January 15, 2003 9:22 AM