ADC ISDN NT11010 - Manual (Page 14)

6
S/T&U LED
The S/T&U LED will flash for a few seconds when the 1010 is first powered on.
This LED will then go off, provided that the S/T & U interfaces are working prop-
erly.
a If there is no ISDN line connected to the U-interface or the line is not acti-
vated, then the S/T&U LED will be on continuously.
b If the U-interface is detected, but is not in sync., the S/T&U LED will flash
eight times per second. In this case, the S/T device will not work until
sync. is restored on the U-interface.
c If the U-interface is in sync., but the S/T-interface is not, then the S/T&U
LED will flash once per second. There must be an S/T device connected to
the S/T-interface before this light will go off.
d Once both the S/T- and U-interfaces are in sync., the S/T&U LED will go
off.
Loopback LED
The U LOOP BACK LED will light only during a telephone company full "2B+D"
loopback test. The ISDN line will not be available until this testing is completed.