Installation guide

4-Port and 8-Port ISDN BRI U Network Modules
Cisco Network Modules Hardware Installation Guide
7-10
In addition, BRI U modules have three LEDs for each port. Two of these LEDs indicate call
activity on the two ISDN BRI B channels, as listed in Table 7-3. The third LED, labeled
NT1, indicates synchronization status of the NT1.
Table 7-3 BRI U Network Modules LEDs
LED Meaning
B1 Activity on B1 channel
B2 Activity on B2 channel
NT1 Synchronous status of NT1