Siemens S5-135U/155U - Manual (Page 548)

B-2
System Manual
C79000-G8576-C199-06
B.1 What is ESD?
All electronic modules are equipped with large-scale integrated ICs or
components. Due to their design, these electronic elements are very sensitive
to overvoltages and thus to any electrostatic discharge.
These Electrostatically- Sensitive Devices are commonly referred to by the
abbreviation ESD.
Electrostatically-sensitive devices are labeled with the following symbol:
!
Caution
Electrostatically-sensitive devices are subject to voltages that are far below the voltage
values that can still be perceived by human beings. These voltages are present if you
touch a component or the electrical connections of a module without previously being
electrostatically discharged. In most cases, the damage caused by an overvoltage is not
immediately noticeable and results in total damage only after a prolonged period of
operation.
Definition
Guidelines for Handling Electrostatically-Sensitive Devices (ESD)