Maintenance; Status Leds - Siemens TC12 Installation, Commissioning And Maintenance Handbook

3.4

MAINTENANCE

3.4.1 Status LEDs

LEDs are provided on the front edge of the board to provide basic status
information. The position of these LEDs and their functions are shown in Figure
30.
The +5 V LED should be on.
If the system fail LED is on, information about the type of fault that has occurred
can be accessed using a handset terminal (see section 3.3.3.27 on handset
commands).
Note: the OTU may still be operating normally, even with the system fail LED
on, depending on the type of failure that has been detected.
If the Watchdog fail LED is illuminated the software is not running correctly. All
transmission from the OTU will be halted and all relay outputs will be set to their
de-energised state. The only way to reset the board is to power off and then on
again.
The Transmit confirm LED is on whilst correctly formatted control messages are
being received by the OTU, and the information is being transferred to the relay
outputs. If a valid control message is not received for four seconds the transmit
confirm LED will go out. Note this LED does NOT indicate that a reply message
has been sent.
The Carrier detect / Rx Data LED should come on once a second for each control
signal on the line. For modem systems this LED indicates carrier is detected on
the line. For RS232 systems where carrier is not required (see GRX command)
the LED indicates data is being received. It does not indicate that the OTU
received a valid control message.
666/HE/43100/000
TC12 Installation, Commissioning & Maintenance Handbook
Page 132 Issue 10