"Excluded Employee" Under The PF Act

Dear Freinds,
Can anyone throw some light on what does the term "excluded employee" means under the PF Act?
As far as what i have learnt from few of my colleagues is that these employees are not covered under the PF act. i.e. their basic salary is more than the prescribed limit mentioned in the PF act. They have an option to opt or not to opt for PF contribution.
Can anyone explain as to what is the prescribed minimum limit as per the PF act?
Best Regards
DS

Kindly advise me, what would be the pross & cons if employees on contractor in catagory of Driver, Office boy - support services are treated for volutray exclusion from PF Coverage, if their PF salary is given more than 6500 from the date of joining.
What would be the procedure to be followed in such case.
Pls. share your openion.
Regards,
Ss