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EXHIBIT 10.23

ADDENDUM I TO LICENSE AGREEMENT

        This agreement (hereinafter "Addendum I") is between Digital Voice
Systems, Inc. a corporation organized under the laws of the Commonwealth of
Massachusetts, with a principal office at One Van de Graaff Drive, Burlington,
MA 01803 (hereinafter called "DVSI") and E. F. Johnson Company a company
incorporated under the laws of the state of Minnesota, with a principal office
at 299 Johnson Avenue, Waseca, Minnesota 56093 (hereinafter called "Licensee").

        This agreement is an addendum to the license agreement between DVSI and
E. F. Johnson Company dated May 15, 1995 (hereinafter the "LICENSE AGREEMENT").
Under the terms of the LICENSE AGREEMENT, Licensee has licensed certain
proprietary IMBE™ Vocoder Technology and Software owned by DVSI for use in APCO
Project 25 hardware products. Licensee desires additional Software for APCO
Project 25 which is capable of real-time implementation of such Technology on a
Texas Instruments TMS320C54X processor (hereinafter the "TMS320C54X Software").
The TMS320C54X Software comprises Object Code but not Source Code. DVSI is
willing to deliver such TMS320C54X Software to Licensee, and to extend the
license granted in the LICENSE AGREEMENT to the TMS320C54X Software under the
terms and conditions described herein.

        This Addendum I becomes effective on the date when it has been signed by
both parties (hereinafter the "Effective Date").

ADDENDUM I

        NOW, THEREFORE, in consideration of the foregoing and the mutual
covenants herein, the parties agree as follows:

1.    DELIVERY OF THE SOFTWARE

1.1DVSI shall, within one (1) month of the Effective Date of this Addendum I, or
upon receipt of the licensing fee under Section 2.1, whichever is later, deliver
to Licensee the TMS320C54X Software which implements the Technology on a Texas
Instruments TMS320C54X processor in a form suitable for installation on an IBM
compatible PC.

1.2In addition, at DVSI's expense, DVSI will make available appropriate
personnel who will provide up to two (2) working days of instruction at DVSI's
facility or on the telephone to familiarize Licensee's staff with the theory and
operation of the programs.

2.    ADDITIONAL PAYMENTS AND RECORDS

        In consideration of the TMS320C54X Software delivered by DVSI under this
Addendum I, Licensee agrees to make the following payments to DVSI.

2.1Licensee shall, upon the Effective Date of this Agreement, pay to DVSI the
sum of thirty thousand United States dollars (U.S. $30,000.00) as an initial
licensing fee.

2.2Licensee shall, within forty five (45) days of the Effective Date of this
Agreement, pay to DVSI the additional sum of thirty thousand United States
dollars (U.S. $30,000.00) as a further licensing fee.

2.3Licensee shall, within ninety (90) days of the Effective Date of this
Agreement, pay to DVSI the additional sum of twenty five thousand United States
dollars (U.S. $25,000.00) as a further licensing fee.

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2.4Should Licensee or its authorized distributors, agents or retailers sell or
lease a system that includes the TMS320C54X Software, Licensee agrees to pay
DVSI a royalty in accordance with the royalty provisions contained in Section 6
of the LICENSE AGREEMENT.

3.    ACCEPTANCE AND TERMINATION

3.1The acceptance criteria for the TMS320C54X Software is that it complies with
the descriptions provided in Section 1.1 of this Addendum I, and Section 4 of
the LICENSE AGREEMENT.

3.2If the TMS320C54X Software does not conform to the specifications in
Section 3.1, Licensee may reject the TMS320C54X Software for technical
non-conformance upon written notification to DVSI within the first thirty
(30) days from the date of Licensee's receipt of the TMS320C54X Software. In the
event that Licensee retains the TMS320C54X Software for a period of thirty
(30) days after delivery of the TMS320C54X Software to Licensee without written
notification to DVSI of rejection, this shall constitute acceptance of the
TMS320C54X Software.

3.3In the event that the TMS320C54X Software is rejected by Licensee in
accordance with Section 3.2, Licensee shall notify DVSI in writing of the
rejection and reasons for rejection. Licensee shall, at DVSI's request,
demonstrate the error(s), failure(s), or area(s) of non-conformance to DVSI on
equipment readily available to DVSI or equipment made available to DVSI either
at DVSI's or Licensee's facility. Errors which cannot be produced on such
equipment shall not be grounds for Licensee's claim that the TMS320C54X Software
does not conform to the specifications in Section 3.1. In the event Licensee
rejects the TMS320C54X Software in accordance with this Section 3, DVSI shall
have thirty (30) days, or longer if mutually agreed, after receiving notice of
such rejection to cure any demonstrated failure(s) or area(s) of non-conformance
in the TMS320C54X Software. Once the TMS320C54X Software has been modified to
cure any demonstrated technical non-conformance, DVSI will deliver the modified
TMS320C54X Software to Licensee and the acceptance/rejection/correction
provisions herein shall be reapplied until the TMS320C54X Software is accepted.

3.4DVSI warrants that the TMS320C54X Software is fully compliant with the
specifications in Section 1.1. DVSI will fix or replace the TMS320C54X Software,
at no cost to the Licensee, if a documented problem is found in the TMS320C54X
Software.

4.    MISCELLANEOUS

4.1The TMS320C54X Software is delivered to Licensee under the licensing terms
and conditions provided under Section 1 of the LICENSE AGREEMENT.

4.2The parties agree that all provisions in the LICENSE AGREEMENT, including the
representation and warranties set forth in Section 7 of the LICENSE AGREEMENT,
which apply to the Technology and the Software shall apply equally to the
TMS320C54X Software.

4.3The parties agree that all provisions of the LICENSE AGREEMENT remain in full
force, and except as specifically stated herein, nothing in this Addendum I
shall be construed to change, modify, nullify or void any of the provision(s) or
condition(s) in the LICENSE AGREEMENT. In the event that any provisions(s) or
condition(s) in this Addendum I are determined to be in conflict with the
LICENSE AGREEMENT, the provision(s) or condition(s) in the LICENSE AGREEMENT
shall take precedence over the provision(s) or condition(s) in this Addendum I.

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4.4Notices.    Any notice or other communication pursuant to this Addendum I
shall be sufficiently made or given on the date of mailing if sent to such party
by certified mail, postage prepaid, addressed to the party to whom notice is
being given at its address below or as it shall designate by written notice
given to the other party.

In the case of DVSI:

Jae S. Lim, Chairman of the Board, or
John C. Hardwick, President
Digital Voice Systems, Inc.
One Van de Graaff Drive
Burlington, MA 01803 USA

In the case of Licensee:

David L. Hattey, General Manager
E. F. Johnson Company
438 Gateway Boulevard
Burnsville, Minnesota 55337

4.5In the event that any provisions of this Addendum I are determined to be
invalid or unenforceable under any controlling body of law, such invalidity or
unenforceability shall not in any way affect the validity or enforceability of
the remaining provisions.

4.6No waiver by either party of any rights hereunder shall be valid unless it is
in writing signed by that party. The omission by either party to insist upon
strict performance of any provision of this Addendum I shall not be construed as
a waiver of such provision.

4.7This Addendum I shall be read and construed according to the laws of the
Commonwealth of Massachusetts, United States of America, and the parties submit
to the jurisdiction of the courts of said Commonwealth.

        IN WITNESS WHEREOF, the parties hereto set their hands and seals and
duly execute this Addendum I as of the last day and year written below.

DIGITAL VOICE SYSTEMS, INC.   LICENSEE
BY:
 
/s/  JOHN C. HARDWICK      

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BY:
 
/s/  DAVID L. HATTEY      

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Typed Name:
 
John C. Hardwick

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Typed Name:
 
David L. Hattey

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Title:
 
President

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Title:
 
General Manager

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Date:
 

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Date:
 

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ADDENDUM I TO LICENSE AGREEMENT
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