Replacing S500 I/O modules while the system is running: The hot swap terminal units TU516-H, TU532-H and TU542-H allow no-load hot swapping of S500 I/O modules during operation. 

• This capability is available for an I/O cluster with the following fieldbuses: PROFIBUS, PROFINET, Modbus TCP.
• Hot swap terminal units can also be used in I/O configurations attached to AC500 CPU modules.
• Hot swap terminal units can be mixed with all normal terminal units (except safety terminal units) in the same configuration, when only specific modules need to be hot swapped.
• The hot swapping feature is also available for extreme condition variants of S500.

• Due to the construction of the S500 system, the wiring remains untouched during hot swap.
• There is no need to remove terminal blocks.
• A S500 I/O module can be removed and replaced while the other modules in the configuration continue operating.
• As soon as a module is re-inserted, it will be configured automatically and put into operation.

• Hot swap is needed in hybrid applications when the control system must not be switched off during the replacement of a module.