Mitsubishi Electric GOT1000 General Description Manual page 3

[DESIGN PRECAUTIONS]
DANGER
Some failures of the GOT, communication unit or cable may keep the outputs
on or off.
An external monitoring circuit should be provided to check for output signals
which may lead to a serious accident.
Not doing so can cause an accident due to false output or malfunction.
If a communication fault (including cable disconnection) occurs during
monitoring on the GOT, communication between the GOT and PLC CPU is
suspended and the GOT becomes inoperative.
For bus connection : The CPU becomes faulty and the GOT becomes
inoperative.
For other than bus connection : The GOT becomes inoperative.
A system where the GOT is used should be configured to perform any
significant operation to the system by using the switches of a device other
than the GOT on the assumption that a GOT communication fault will occur.
Not doing so can cause an accident due to false output or malfunction.
Do not use the GOT as the warning device that may cause a serious accident.
An independent and redundant hardware or mechanical interlock is required
to configure the device that displays and outputs serious warning.
Failure to observe this instruction may result in an accident due to incorrect
output or malfunction.
Incorrect operation of the touch switch(s) may lead to a serious accident if the
GOT backlight is gone out.
When the GOT backlight goes out, the POWER LED flickers (green/orange)
and the display section turns black and causes the monitor screen to appear
blank, while the input of the touch switch(s) remains active.
This may confuse an operator in thinking that the GOT is in "screensaver"
mode, who then tries to release the GOT from this mode by touching the
display section, which may cause a touch switch to operate.
Note that the following occurs on the GOT when the backlight goes out.
• The POWER LED flickers (green/orange) and the monitor screen appears
blank
A-2