Exhibit 10.12

                         Promissory Note


                                        Chicago, Illinois: 
                                         April 17, 1996



     On the earlier of April 16, 1997 (the "Termination Date") or
demand, for value received, Tellabs, Inc.  (the "Borrower")
hereby promises to pay to the order of BANK OF AMERICA ILLINOIS
(the "Bank"), the principal sum of FIFTY  MILLION AND NO/100
DOLLARS ($50,000,000.00) or, if less, the aggregate unpaid
principal amount of all Advances made by the Bank to the
undersigned hereunder.  The initial Advance, all subsequent
Advances and all payments made on account of principal  will be
recorded by the holder in its records.  Capitalized terms used
herein and not otherwise defined herein shall have the meanings given
such terms in the Loan Agreement, hereinafter defined. 


     The Borrower further promises to pay to the order of the Bank
interest on the aggregate unpaid principal amount of this Note
outstanding from time to time, from the date of this Note until paid in
full, at the rates per annum which shall be determined in accordance
with the provisions of the Loan Agreement.  Accrued interest shall be
payable on the dates specified in the Loan Agreement.


     All payments of principal and interest under this Note shall be
made in lawful money of the United States of America in
immediately available funds at the Bank's office at 231 South
LaSalle Street, Chicago, Illinois  60697, or at such other place
as may be designated by the Bank to the Borrower in writing.


     This Note is the Note referred to in, and evidences
indebtedness incurred under, a Demand Loan Agreement (as it may
be amended, modified or supplemented from time to time, the
"Loan Agreement"), dated as of April 17, 1996, between the
Borrower and the Bank, to which Loan Agreement reference is made
for a statement of the terms and provisions thereof.


     All parties hereto, whether as makers, endorsers or otherwise,
severally waive presentment, demand, protest and notice of
dishonor in connection with this Note.













     This Note is governed by the internal laws of the State of
Illinois.



                                   TELLABS, INC.





                                   By: s\ Michael J. Birck 
                                        ____________________  

                                        Michael J. Birck  
                                        President and Chief 
                                        Executive Officer




                                    By: s\ Peter Guglielmi 
                                        ____________________  
                                        Peter Guglielmi  
                                        Chief Financial Officer



                                        1000 Remington Boulevard 
                                        Bolingbrook, Illinois 60440


                             Attention: Mr. Michael J. Birck

                                        President and Chief
                                        Executive Officer


                            Telephone:

                            Fax No.: