Effect Of Incorrect Switch Settings On The Modem Pcb - Siemens TC12 Installation, Commissioning And Maintenance Handbook

This controls what signals can cause the low frequency audio alarm to sound. If it
is incorrectly set, the alarm may sound for reasons other than those expected or
may not sound when expected.
(3) S3 - Audio ON/OFF
If the audio alarm does not sound when expected check that this switch is set
correctly. If it is set to off the audio off LED, on the front of the PCB, will be
illuminated.
(4) Alarm Volume Control (RV1)
If the Audio alarm volume control is set too low it may not be possible to hear the
audio alarm.

2.4.3 Effect of Incorrect Switch Settings on the Modem PCB

(1) SW1 - Mode Select Switch
If this is set incorrectly the four modems on the modem PCB may not work at all or
will be set to a spurious mode. The yellow LED (request to send) may light for
each modem, but the green LED (carrier detect) may not.
(2) SW2, SW3, SW6 and SW7 - Line Level Switches
SW2 and SW3 are 8-way switches used to set line levels for modem 1 and
modem 2 on the Modem PCB. If switch positions 1 to 4, of the DIL switch, are set
incorrectly the particular modem will transmit at the wrong output power.
WARNING - FOR UK USAGE THE OUTPUT POWER MUST NOT BE SET TO
If switch positions 5 and 6 are set incorrectly the receive threshold for the
particular modem will be wrong. If it is set too low, corrupted reply messages may
occur, in which case reply too early errors may be displayed on the TCC. If set too
high the reply messages from the OTUs may be undetected - the yellow LED will
light for the appropriate modem but the green LED will not.
If Switch position 7 is set open, there will be no Control Signal on the line. The
yellow LED will light but the green LED will not light.
If Switch position 8 is set open, there will be no Reply Signal on the line. The
yellow LED will light but the green LED will not light.
SW6 and SW7 are 6-way DIL switches used to set line levels for modem 3 and
modem 4 on the Modem PCB. Incorrect setting of these switches will have the
same effect on these modems, as switch positions 1 to 6 described above.
(3) SW4 - 2/4 Wire Selector Switch
a) 4 wire system but with 2 wire selected in error:
No reply messages will be received. In Full duplex mode the yellow and green
LED for the modem will come on simultaneously every second. In half duplex
mode only the yellow LED will come on.
666/HE/43100/000
TC12 Installation, Commissioning & Maintenance Handbook
GREATER THAN –13 dBm.
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