Siemens SIMATIC ET 200M Operating Instructions Manual page 255

Equipotential bonding
Electrical connection (equipotential bonding conductor) that places electrical equipment
parts and non-equipment related conductive parts at equal or nearly equal potential to
prevent interfering or hazardous voltage between them.
Fault-tolerant system
A fault-tolerant system (also called H system, an abbreviation of the German
'Hochverfügbares System') consists of two or more CPUs or two or more separate devices,
such as PCs (master / reserve). The user program is processed identically in master and
reserve.
Fiber-optic cable
Fiber-optic cables are made from fibere-optics or plastic and have an extremely high
transmission rate. They are resistant to electromagnetic interference and practically tap-
proof.
FREEZE
is a control command that is issued by the DP master to a set of DP slaves.
Upon receiving the FREEZE control command the DP slave freezes the inputs at their current
states and transfers them to the DP master in cycles.
After each received FREEZE the DP slave freezes the input state again.
The DP slave will cyclically transfer the input data to the DP master only after the DP master
has issued the UNFREEZE control command.
Functional grounding
This grounding method is used to ensure that the electrical product is functioning as
expected. Functional grounding short-circuits any noise voltage that might render a product
impermissible.
Ground
Conductive ground has an electrical potential of zero.
Close to ground electrodes the ground's potential might be different from zero. The term
"reference ground" is frequently used to describe this situation.
Ground-free
No galvanic connection to → ground
ET 200M
Operating Instructions, 04/2022, EWA-4NEB7806006-09
Glossary
255