Nortel Networks DCT1900 - Manual (Page 365)

Technical Product Manual - DCT1900
Maintenance, Fault Signalling
Maint-DCT1900/R8/mw 3-5
© 2000-2005
Fig 3–1 LEDs in the System
3.7.1 LEDs on System Boards
Each board has four LEDs at the top. The SLU has two times four LEDs because it consists of a
SPU and a CLU on one board, each with its own board controller and board address. The DTU
also has two times four LEDs because it contains a duplication of circuits with two board
controllers, each with their own address.
LED 1
LED 1 is the "board powered" LED, illuminating when the board is powered. On all boards this
green LED shall be on.
LED 2
LED 2 is the "watch–dog reset" LED, illuminating when the board controller receives a watch–dog
reset. This LED normally only flashes during the power–on and 24–Hour test when the watch–dog
circuit is being tested.
LED 3
LED 3 is the "board not polled" LED, illuminating when the board has not been polled by the CPU
poll processor for a period of time. As a result the CPU may not know the board any more, giving it
the state of PNP.
LED 4
LED 4 is the "error" LED, generally indicating an error on the board. On the CLU, the CLU part of
the SLU board, and the DTU boards, this LED can be active for other reasons. Therefore, it may
not always be taken as an error indicator.
A CLU board or the CLU part of an SLU board will light LED 4 when Base Stations are in NEW
state, which means that a delay value is not yet programmed. The LED will turn off automatically
after programming the last Base Station of the CLU or if one Base Station is connected at a time,
the LED will turn off when added via CSM.
A DTU will light LED 4 when no trunk is connected. The DTU has no error, but the LED indicates
that no external clock is detected. The LED turns off as soon as a trunk is connected.