3Com NBX 100 Installation Manual page 161

Verifying the T1 Digital Line Card 161
For a complete description of the status lights on the front of the card,
see "T1 Digital Line Card" on page 36.
You are now ready to configure the T1 Digital Line Card for either DS1
signaling or ISDN PRI signaling. See Chapter 2, "Device Configuration,"
in the NBX Administrator's Guide for instructions.