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

2.4

MAINTENANCE

2.4.1 Status LEDs

LEDs are provided on the front edge of the Modem Board and PSU Board to
provide basic status information. The position of these LEDs and their functions
are shown in Figure 16.
All power LEDs on the modem PCB should be ON.
The yellow transmit LEDs indicate that the particular modem has received a
request to send. In normal working this means that the control signal is being
transmitted on the line. However if switches/cables have been set up incorrectly
the LED may be ON, without the control signal actually reaching the line. All yellow
LEDs on all modem PCBs should go on together (though not necessarily go off at
the same time) once per second.
The green receive LED (Carrier detect) should come on once for every OTU which
replies on the line during the second (the LED is set by the modem carrier detect
output and does not indicate that the carrier detected was a valid reply message).
The PC power LED on the PSU PCB should be ON. IF it is OFF then there is a
fault, however no audible alarms will sound and no LEDs will illuminate on SIP
panel if the PC has no power.
The Digital output PCB has two status LEDs. The top LED indicates that the
Power to the board is OK (5 V supply from PSU PCB).
The second LED on the digital output PCB indicates a watchdog fail. If this occurs
all digital outputs are switched off on that board.
666/HE/43100/000
TC12 Installation, Commissioning & Maintenance Handbook
Modem PCB
PSU PCB
Digital Output PCB
Page 47 Issue 10