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2.2 System behaviour after a power failure
If the UPS output supplies the system with power, the computer boots
and starts its operating system. Meanwhile the Serial Watchdog runs its
initialisation procedure and waits for commands which are sent via the
serial port. At this time the POWER-LED is on, the COMMUNICATION-
LED is off and the STATE-OF-HEALTH-LED shines red. If the 1H-
jumper (located at the watchdog's electronic board, see figure 2) is not
closed and no command is received, the watchdog stays in this state as
long as power is available. If the 1H-jumper is closed and no command
is received within 1 hour after initialisation, the watchdog will open the
power relay after 1 hour of waiting. This option is very useful in cases
where the operating system hangs during its startup. After 1 hour the
watchdog tries to start the computer a second time by breaking the
computer's power supply for a short time. This procedure repeats for
further 2 times if the computer hangs permanently. If this option is
enabled, the operator should take care during computer maintenance
works. The computer will crash exactly one hour after booting if the
operator forgets to send the STOP-command to the watchdog!
Figure 2
Location of the 1H-Jumper