December 13, 1999


Westell Technologies, Inc.
750 North Commons Drive
Aurora, IL

Gentlemen:

                  Reference is made to the 6% Subordinated Convertible Debenture
("Debenture")  dated April 15, 1999 in the principal amount of $9,000,000 issued
by Westell  Technologies,  Inc. ("Company ") to Castle Creek Technology Partners
LLC ("Investor") and the Stock Purchase Warrant  ("Warrant")  issued to Investor
by the Company dated April 15, 1999 for the right to purchase  409,091 shares of
the Company Class A common stock.

         Section 4(e) of the Warrant provides that in the event of certain Major
Transactions (as defined  therein),  the holder of the Warrant shall be entitled
to either  (A)  retain  the  warrant  pursuant  to the  clause  (a) of the first
sentence of Section 4(e) or (B) receive specified  consideration in exchange for
the  Warrant  pursuant  to clause  (b)(i) or  (b)(ii) of the first  sentence  of
Section 4(e).

         Section  8.3 of the  Debenture  provides  that in the event of  certain
Major  Transactions (as defined  therein),  the holder of the Debenture shall be
entitled  at its option to receive  specified  consideration  for the  Debenture
pursuant to clause (i) or (ii) of the first sentence of Section 8.3.

                  This  Letter  Agreement  documents  the  following  agreements
between Investor and the Company:

         1. In  consideration  of the reduction in Exercise Price (as defined in
the  Warrant)  described  in  paragraph  2 of this  Letter  Agreement,  Investor
irrevocably  waives any right to receive any  consideration  specified in clause
(b)(ii)  of  the  first  sentence  of  Section  4(e)  of  the  Warrant  and  any
consideration  specified in clause (ii) of the first  sentence of Section 8.3 of
the  Debenture in  connection  with any Company  Transaction  (as defined in the
Warrant and the Debenture)  which is first announced  within sixty days from the
date hereof in which the shares issued in the transaction to shareholders of the
other party do not exceed 41% (on an after  issuance  basis) of the  outstanding
common stock of both classes of the Company.

         2. The  Warrant  is hereby  amended to reduce  the  Exercise  Price (as
defined in the Warrant) from $8.9208 to $5.9208,  subject to further  adjustment
from time to time in accordance with the Warrant. The number of shares of Common
Stock  issuable  upon exercise of the Warrant shall not be adjusted by reason of
the reduction in Exercise Price





effected  by this  Paragraph  2; and there  shall be no further  Exercise  Price
adjustment  pursuant  to  Section  4(a) of the  Warrant  on account of a Company
Transaction  which is subject to the waiver of  Paragraph  1. There  shall be no
adjustment  to the  Conversion  Price of the  Debenture by virtue of the Warrant
Exercise Price adjustment herein.

         3. The  Investor  hereby  releases  and waives any claims  against  the
Company for Warrant  Exercise Price  adjustments or Debenture  Conversion  Price
adjustments  which arise or could arise or be assertable by reason of any action
or occurrence under Section 8.10 of the Debenture or Section 4(l) of the Warrant
from April 15, 1999 through the date of this Letter Agreement.

         4. Each party  represents  and warrants to the other that the execution
of this Letter Agreement by it has been authorized by all necessary  corporation
action,  including,  for the  Company,  by its Board of  Directors.  This Letter
Agreement  shall  constitute  an amendment to both the Debenture and the Warrant
and shall bind successor holders to the Debenture and the Warrant and successors
to the  Company.  The Company  shall not be required to register any transfer of
the  Debenture  or Warrant  unless the  transferee  acknowledges  the  amendment
thereto under this Letter Agreement.

         5. The undersigned  acknowledge  that the Company intends to enter into
agreements  ("Other  Agreements")  with the other holders  ("Other  Holders") of
warrants  and  debentures  issued on April 15,  1999 which  address  the matters
covered by this Letter  Agreement.  There shall be no  adjustment to the Warrant
Exercise Price or the Debenture  Conversion Price on account of execution of the
Other Agreements. The Company covenants that in the event that the provisions of
this Letter  Agreement  are not  substantially  as  beneficial  to Investor (but
reflecting the relative  holdings of warrants and debentures of Investor and the
Other Holders) as the provisions contained in any of the Other Agreements,  then
the Investor may upon  written  notice to the Company  given within five days of
receipt of a copy of the Other  Agreements  elect to be governed by the terms of
such more favorable Other Agreement  (adjusted for relative  holdings),  and the
Company shall enter with Investor into a modification  of this Letter  Agreement
to reflect all of the terms of such Other Agreement.

                                        Castle Creek Technology Partners LLC
                                        By Castle Creek Partners LLC,
                                        Investment Manager

                                        By /s/John Ziegelman
                                           -----------------

Westell Technologies, Inc.

By /s/Marc Zionts, Executive Vice President
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