This article relates to Cisco TelePresence Management Suite.
Q. When I open the phone book from my endpoint and open a folder, no ISDN numbers are shown for entries that should have ISDN
A. TMS will only show phone book entries if there is a valid call route between your system and the calling information in the phonebook entry.
If no ISDN numbers are shown, TMS cannot register that your endpoint can make ISDN calls.