Omron CJ1W-CT021 Operation Manual page 15

Safety Precautions
!WARNING
!WARNING
!WARNING
!WARNING
!Caution
!Caution
!Caution
• The PLC outputs may remain ON or OFF due to deposits on or burning of the
output relays, or destruction of the output transistors. As a countermeasure for
such problems, external safety measures must be provided to ensure safety in
the system.
• When the 24-VDC output (service power supply to the PLC) is overloaded or
short-circuited, the voltage may drop result in the outputs being turned OFF. As
a countermeasure for such problems, external safety measures must be pro-
vided to ensure safety in the system.
The CPU Unit refreshes I/O even when the program is stopped (i.e., even in
PROGRAM mode). Confirm safety thoroughly in advance before changing the
status of any part of memory allocated to I/O Units, Special I/O Units, or CPU
Bus Units. Any changes to the data allocated to any Unit may result in unex-
pected operation of the loads connected to the Unit. Any of the following opera-
tion may result in changes to memory status.
• Transferring I/O memory data from a Programming Device to the CPU Unit.
• Changing present values in memory with a Programming Device.
• Force-setting/-resetting bits with a Programming Device.
• Transferring I/O memory files from a Memory Card or EM file memory to the
CPU Unit.
• Transferring I/O memory from a host computer or from another PLC on a net-
work.
Do not attempt to take any Unit apart while the power is being supplied. Doing so
may result in electric shock.
Do not touch any of the terminals or terminal blocks while the power is being
supplied. Doing so may result in electric shock.
Do not attempt to disassemble, repair, or modify any Units. Any attempt to do so
may result in malfunction, fire, or electric shock.
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.
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.
Tighten the screws on the terminal block of the AC Power Supply Unit to the
torque specified in the operation manual. Loose screws may result in burning or
malfunction.
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