Maintenance; Status Leds; Effect Of Incorrect Switch Settings On The Otu Pcb - Siemens TC12 Installation, Commissioning And Maintenance Handbook

6.5

MAINTENANCE

6.5.1 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
34.
A System fail on the Controller Main Processor PCB may indicate a fault on the
Integral OTU PCB.
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 6.4.2 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 and all
transmission from the OTU will be halted. 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
controller. If a valid control message is not received for 4 seconds the transmit
confirm LED will go out. Note this LED does NOT indicate that a reply message
has been sent.
The Carrier detect LED should come on once a second for each control signal on
the line (the LED is set by the software in response to the modem carrier detect
output being set, it does not indicate that the carrier detected was a valid control
message).

6.5.2 Effect of Incorrect Switch Settings on the OTU PCB

(1) S1 - 2/4 Wire Select Switch
4 wire system but with 2 wire selected in error or 2 wire system but with 4 wire
selected in error; the OTU may not receive the control signal and will not reply,
therefore the carrier detect and transmit confirm LEDs will be OFF.
(2) S2 - Lithium Battery On/Off Switch
If this switch is off the system fail LED will illuminate on the Controller Main
Processor PCB and the Integral OTU will not communicate with the Instation.
(3) S3 - Line level switch
A 6-way DIL switch is used to set line levels. If switch positions 1 to 4, of the DIL
switch, are set incorrectly the OTU will transmit at the wrong output power.
If switch positions 5 and 6 are set incorrectly the receive threshold for the OTU
modem will be wrong. If it is set too low corrupted control messages may occur. If
set too high the control messages from the Instation may be undetected.
666/HE/43100/000
TC12 Installation, Commissioning & Maintenance Handbook
Page 191 Issue 10