3 How FRITZ!Card Works
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3.2 How Does an ISDN-Controller Work?
An ISDN-Controller serves as the connection between ISDN and
your computer. The ISDN cable supplied connects to the S
O
bus
and thus to the local exchange of the telephone network.
Incoming data are transmitted to the computer for use in
application programs through the PC interface (e.g., PCI/ISA/
USB). The multitude of potential implementations in ISDN, from
telephony through faxing to Internet, demand high efficiency
and quality from the device driver and interfaces.
Any service, for intance telefax, is realized using “protocols”.
Protocols stipulate the procedures used for data transmission
between the parties. They facilitate smooth communication and
determine such factors as transfer speed or data compression
during transmission. Both communications partners must
support the protocol to be implemented, for example, T.30 for
Group 3 fax or HDLC transparent for Internet. The driver software
for the ISDN-Controller FRITZ!Card must support the right
parameters in real time for each ISDN connection and must
forward these both to local applications and to the remote
partner. The data are handed over to the computer’s
communication software via COMMON ISDN API interface, CAPI
for short. CAPI establishes the connection between the ISDN-
Controller and the installed applications like FRITZ!. Thus the
driver software for the ISDN-Controller FRITZ!Card is also called
the CAPI driver.
Although every FRITZ!Card has a special CAPI driver for each
operating system supported, the applications function
identically and generally are based on CAPI 2.0. The modules of
the FRITZ! communications software are also based on CAPI 2.0,
as are other a number of programs from other manufacturers.
AVM provides the system drivers AVM ISDN CAPI Port Driver and
NDIS WAN CAPI Driver for programs which require a modem or a
network adapter.
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