System.ServiceModel.Configuration.MachineSettingsSection does not exist

Based on the instructions in this link for enabling logging of PII...

https://msdn.microsoft.com/en-us/library/ms730318(v=vs.90).aspx

None my versions - 3.5 -4.5.1 of .NET has a class System.ServiceModel.Configuration.MachineSettingsSection

The only class with that name that exists is System.Transactions.Configuration.MachineSettingsSection

I can only assume this is why it is not possible to add that section to machine.config, can anybody confirm this please?

If so, then where should this section go in machine.config to enable PII logging?

Thanks

Jon