TC12 Installation, Commissioning & Maintenance Handbook
2.4 MAINTENANCE
2.4.1
LEDs are provided on the front edge of the Modem Board and PSU Board to
p rmation s and their functions
are shown in Figure 16.
A power LEDs on the modem P
quest to send. In normal working this means that the control signal is being
the line. All yellow
off at
come on once for every OTU which
plies 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).
o LEDs will illuminate on SIP
anel if the PC has no power.
ital Output PCB
ard is OK (5 V supply from PSU PCB).
The second LED on the digital output PCB indicates a watchdog fail. If this occurs
Status LEDs
rovide basic status info . The position of these LED
Modem PCB
ll CB should be ON.
The yellow transmit LEDs indicate that the particular modem has received a
re
transmitted on the line. However if switches/cables have been set up incorrectly
the LED may be ON, without the control signal actually reaching
LEDs on all modem PCBs should go on together (though not necessarily go
the same time) once per second.
The green receive LED (Carrier detect) should
re
PSU PCB
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 n
p
Dig
The Digital output PCB has two status LEDs. The top LED indicates that the
Power to the bo
all digital outputs are switched off on that board.
666/HE/43100/000 Page 47 Issue 9