Hitachi HSC-2100 Hardware Manual page 15

(chapter 6, page 6-2)
Do not touch any of the modules in the programmable controller when they are
in an energized state. Touching any of the modules in an energized state
may lead to a discharge of static electricity from your body to the module,
resulting in malfunction or breakage of the module. If you have no choice but
to touch such a module, be sure to discharge the static electricity by touching
the metal frame of the cubicle and then touch the module. This is also true
when you perform any of the following actions on a module in its non-
energized state: 1) setting a switch on the module; 2) connecting or
disconnecting the cable from the module; or 3) inserting or removing the
connector from the module.
Every fixing or terminal screw must be secured tightly.
Insufficiently tightened screws may result in malfunction, smoke, or fire.
(chapter 6, page 6-4)
If the input voltage to a power supply module is close to the upper or lower
limit of the prescribed range, ask a power supply management specialist to
perform an inspection even if the input voltage is within the operating
specifications.
Power to the I/O modules mounted in the cubicle must be supplied from a
power supply module with an appropriate wattage rating for the I/O modules.
If a power supply module whose wattage rating is lower than expected is used,
it may result in a fire.
Be sure to power down your application system before replacing an existing
module.
Replacing a module in a power-on condition may cause damage to the
hardware.
NOTICE
NOTICE
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