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Safety Precautions 3
!WARNING Do not touch any of the terminals or terminal blocks while the power is being
supplied. Doing so may result in electric shock.
!WARNING Do not attempt to disassemble, repair, or modify any Units. Any attempt to do
so may result in malfunction, fire, or electric shock.
!WARNING Do not touch the Power Supply Unit while power is being supplied or immedi-
ately after power has been turned OFF. Doing so may result in electric shock.
!WARNING Provide safety measures in external circuits (i.e., not in the Programmable
Controller), including the following items, to ensure safety in the system if an
abnormality occurs due to malfunction of the PLC or another external factor
affecting the PLC operation. Not doing so may result in serious accidents.
• Emergency stop circuits, interlock circuits, limit circuits, and similar safety
measures must be provided in external control circuits.
• The PLC will turn OFF all outputs when its self-diagnosis function detects
any error or when a severe failure alarm (FALS) instruction is executed.
As a countermeasure for such errors, external safety measures must be
provided to ensure safety in the system.
• The PLC outputs may remain ON or OFF due to deposition or burning of
the output relays or destruction of the output transistors. As a counter-
measure for such problems, external safety measures must be provided
to ensure safety in the system.
• When the 24-V DC output (service power supply to the PLC) is over-
loaded or short-circuited, the voltage may drop and result in the outputs
being turned OFF. As a countermeasure for such problems, external
safety measures must be provided to ensure safety in the system.
!Caution Confirm safety before transferring data files stored in the file memory (Mem-
ory Card or EM file memory) to the I/O area (CIO) of the CPU Unit using a
peripheral tool. Otherwise, the devices connected to the output unit may mal-
function regardless of the operation mode of the CPU Unit.
!Caution Fail-safe measures must be taken by the customer to ensure safety in the
event of incorrect, missing, or abnormal signals caused by broken signal lines,
momentary power interruptions, or other causes. Abnormal operation may
result in serious accidents.
!Caution Interlock circuits, limit circuits, and similar safety measures in external circuits
(i.e., not in the Programmable Controller) must be provided by the customer.
Abnormal operation may result in serious accidents.
!Caution Execute online edit only after confirming that no adverse effects will be
caused by extending the cycle time. Otherwise, the input signals may not be
readable.
!Caution Confirm safety at the destination node before transferring a program to
another node or changing contents of the I/O memory area. Doing either of
these without confirming safety may result in injury.
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