If an ISDN line has been installed to do QuickTime Conferencing from a Macintosh with an installed H.320 card, be sure your ISDN provider has provided the correct line termination type/mode. The ISDN provider may supply your ISDN line with generic type/mode termination, when video conferencing type/mode termination is required.
To illustrate, an ISDN line to be used with QuickTime Conferencing was supplied, and after many attempts (different configurations, computers, H.320 cards, and phone numbers) this line would not work properly.
In an attempt to resolve this issue, the system was connected to a known working ISDN line to check the system's configuration and hardware, and everything worked properly. The ISDN provider, of the non-working line, was contacted and the line termination was changed from type/mode "D" (generic) to "A". The ISDN line now works properly.
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