acf confidence intervals in ARMA

I tried to understand the two formulas below by google
and books I have but have no success so far.

?plot.acf
Confidence limits assume a white noise input by default.

? ? "The confidence interval plotted in 'plot.acf' is based on an
? ? ?_uncorrelated_ series and should be treated with appropriate
? ? ?caution. ?Using 'ci.type = "ma"' may be less potentially
? ? ?misleading."

HTH,

pcc

Peter Carl
145 Scottswood Rd
Riverside, IL 60546
312 307 6346
http://www.braverock.com/~peter