<PAGE>
                                                                      Exhibit 24
                                POWER OF ATTORNEY

         Each of the undersigned officers and directors of Applied Innovation
Inc., a Delaware corporation (the "Company"), hereby appoints Gerard B.
Moersdorf, Jr. and Curtis A. Loveland as his true and lawful attorneys-in-fact,
or any of them, with power to act without the other, as his true and lawful
attorney-in-fact, in his name and on his behalf, and in any and all capacities
stated below, to sign and to cause to be filed with the Securities and Exchange
Commission the Company's annual report on Form 10-K, for the fiscal year ended
December 31, 2003, and any and all amendments thereto, hereby granting unto said
attorneys, and to each of them, full power and authority to do and perform in
the name and on behalf of the undersigned, in any and all such capacities, every
act and thing whatsoever necessary to be done in and about the premises as fully
as each of the undersigned could or might do in person, hereby granting to each
such attorney full power of substitution and revocation, and hereby ratifying
all that either such attorney or his substitute may do by virtue hereof.

         IN WITNESS WHEREOF, the undersigned have executed this Power of
Attorney in counterparts if necessary, effective as of February 27, 2004.

DIRECTORS/OFFICERS:

<TABLE>
<CAPTION>
                  Signature                                                     Title
                  ---------                                                     -----
<S>                                                     <C>
/s/ Gerard B. Moersdorf, Jr.                                  Chairman of the Board, President and Chief
-------------------------------------                         Executive Officer
         Gerard B. Moersdorf, Jr.                             (Principal Executive Officer)


/s/ Michael P. Keegan                                         Executive Vice President and Chief Operating Officer
--------------------------------------------                  (Principal Financial and Principal Accounting Officer)
         Michael P. Keegan


 /s/ Michael J. Endres                                        Director
--------------------------------------------
         Michael J. Endres

 /s/ Thomas W. Huseby                                         Director
--------------------------------------------
         Thomas W. Huseby

 /s/ William H. Largent                                       Director
--------------------------------------------
         William H. Largent

/s/ Curtis A. Loveland                                        Director
--------------------------------------------
         Curtis A. Loveland

/s/ Richard W. Oliver                                         Director
--------------------------------------------
         Richard W. Oliver

/s/ John D. Riedel                                            Director
--------------------------------------------
         John D. Riedel

/s/ Alexander B. Trevor                                       Director
--------------------------------------------
         Alexander B. Trevor
</TABLE>


                      Applied Innovation Inc. | Form 10-K