Document:

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                                                                   EXHIBIT 10.16

                                 PROMISSORY NOTE

$XXXXXX
Victoria, Minnesota
April 2, 2001

FOR VALUE RECEIVED, the undersigned, XXXXX with an address of XXXXXXXXXXXXXXXXX
("Maker") hereby promises to pay to the order of HEI, Inc., with an address of
1495 Steiger Lake Lane, Victoria, Minnesota, 55386, ("Holder") the principal sum
of XXXXXXXXX dollars ($XXXXXX), together with interest in arrears on the unpaid
principal balance from the date hereof at 8.25% per annum in accordance with
this promissory note ("Note"). Said sum shall be paid in the following manner:

The term of this Note is five (5) years. Interest only payments shall be made
annually (April 2, 2002 and April 2, 2003) for the first two (2) years and
annual installments of principal and interest for the next three (3) years shall
be made thereafter, in accordance with the attached Schedule A. All payments
shall be first applied to interest then principal. This note may be prepaid, at
any time, in whole or in part, without penalty.

This Note is executed by Maker to evidence its indebtedness to Holder arising
out of the purchase by Maker of certain common shares of the Holder through the
exercise of stock options.

This note shall be at the option of any holder thereof be immediately due and
payable upon the occurrence of any of the following:

1)   Failure to make any payment due hereunder within on or before its due date.

2)   Breach of any condition of any security interest, mortgage, loan agreement,
     pledge agreement or guarantee granted as collateral security for this note.

3)   Upon the death, incapacity, dissolution or liquidation of any of the
     undersigned, or any endorser, guarantor to surety hereto.

4)   Upon the filing by any of the undersigned of an assignment for the benefit
     of creditors, bankruptcy or other form of insolvency, or by suffering an
     involuntary petition in bankruptcy or receivership not vacated within
     thirty (30) days.

5)   Upon the cessation of the employment relationship or board membership,
     whether voluntary or involuntary, between the undersigned and Holder.

6)   Upon the sale of the Holder shares purchased with the monies borrowed on
     this Note, a pro rata percentage of the number sold to the total amount
     originally purchased shall become due and payable.

The Maker represents that he has the financial ability to repay the obligations
due on this Note as they are stated on the attached Schedule A.

In the event this note shall be in default and placed for collection, then the
undersigned agrees to pay all reasonable attorney fees and costs of collection.
Payments not made within five (5) days of due date shall be subject to a late
charge of 1% per month of said payment. All payments hereunder shall be made to
such address as may from time to time be designated by any holder.

The undersigned agrees to remain fully bound until this note shall be fully paid
and waives demand, presentment and protest and all notices hereto and further
agrees to remain bound notwithstanding any extension, modification, waiver, or
other indulgence or discharge or release of any obligor hereunder or exchange,
substitution, or release of any collateral granted as security for this note. No
modification or indulgence by any holder hereof shall be binding unless in
writing; and any indulgence on any one occasion shall not be an indulgence for
any other or future occasion. Any modification or change in terms, hereunder
granted by any holder hereof, shall be valid and binding upon the undersigned,

                                       1

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notwithstanding the acknowledgement of the undersigned. The rights of any holder
hereof shall be cumulative and not necessarily successive. This note shall take
effect as a sealed instrument and shall be construed, governed and enforced in
accordance with the laws of the State of Minnesota.

IN WITNESS WHEREOF, this Note is executed under seal on the day, month and year
first above written.

                                             -----------------------------------

ACKNOWLEDGEMENT

Acknowledged and agreed to by:

HEI, Inc.

By:
   ------------------------------------
Name:
     ----------------------------------
Title:
      ---------------------------------

                                       2Form of Subscription

 

Exhibit 4.1

[Form of Subscription Warrant]

Warrant No.:__________

        The Terms and Conditions of the Rights Offering are Set Forth in
ISCO International, Inc.'s Prospectus Dated _____, 2001 (the “Prospectus”) and are Incorporated
Herein By Reference. Copies of the Prospectus are Available Upon Request from
MacKenzie Partners, Inc. as
the Information Agent.

	Stockholder Name and Address:	Rights to Purchase Shares of
	 	Common Stock of ISCO
	______________________________
	______________________________	_____________
	______________________________

ISCO International, Inc.

Subscription Warrant

Evidencing Non-Transferable Subscription Rights To Purchase Shares of the

Common Stock of ISCO International, Inc.

Subscription Price: $_____ Per Share

Void if Not Exercised Before the Expiration Date (as defined in the Prospectus)

        ISCO International, Inc. (“ISCO”) is conducting a rights offering (the
“Rights Offering”), which entitles the holders of shares of ISCO’s common stock
(the “Common Stock”), as of the close of business on _____, 2001 (the “Record
Date”) to receive _____ rights (each, a “Right”) for each share of Common Stock
held of record on the Record Date. Holders of Rights are entitled to subscribe
for and purchase _____ share of Common Stock for each _____ Right (the “Basic
Subscription Privilege”) at a subscription price of $___ per share (the
“Subscription Price”). If any shares of Common Stock are not purchased by
holders of Rights pursuant to the Basic Subscription Privilege, any holder
exercising its Basic Subscription Privilege in full may purchase an additional
number of available Shares up to a maximum number of shares equal to twice the
number of shares purchased under the Basic Subscription Privilege, if so
specified in such holder’s subscription documents, subject to proration (the
“Oversubscription Privilege”). No fractional Rights or cash in lieu thereof
will be issued or paid. If the number of shares of Common Stock held on the
Record Date would result in the receipt of fractional Rights, the number of
Rights shall be rounded down to the nearest whole number. As a result, ISCO
stockholders that held of record fewer than _____ shares on the Record Date are
not eligible to purchase shares in this Rights Offering. Set forth above is
the number of Rights to which such holder is entitled pursuant to the Basic
Subscription Privilege (rounded down, if applicable, to the nearest whole
share).

        This Subscription Warrant (or a Notice of Guaranteed Delivery) must be
received by LaSalle Bank N.A. together with payment in full of the Subscription
Price by 5:00 p.m. New York City time, on or before _____, 2002, unless the
subscription period for this Rights Offering is extended in the sole discretion
of the Company (the “Expiration Date”). Any Rights not exercised prior to the
Expiration Date will be null and void. Any subscription for shares of Common
Stock in this Rights Offering made hereby is irrevocable.

 

 

        The Rights represented by this Subscription Warrant may be exercised by
duly completing Form 1 and, if you are exercising Rights through your bank or
broker, Form 2 on the back of this Subscription Warrant. Rights holders are
advised to review the Prospectus and instructions, copies of which are
available from MacKenzie Partners, Inc., before exercising their Rights.

        Rights holders should be aware that if they choose to exercise only part
of their Rights, they may not receive a new Subscription Warrant in sufficient
time to exercise the remaining Rights evidenced thereby.

2

 

FORM 1

(on reverse of Subscription Warrant)

        EXERCISE AND SUBSCRIPTION:   The undersigned hereby irrevocably exercises
one or more Rights to subscribe for shares of Common Stock as indicated below,
on the terms and subject to the conditions specified in the Prospectus, receipt
of which is hereby acknowledged.

        (a)  Number of whole shares subscribed for pursuant to the Basic
Subscription Privilege:

_____________ Rights x $____ = $______________.

(One Right is required to subscribe for ___ share.)

        (b)  Number of whole shares subscribed for pursuant to the Oversubscription Privilege*:

__________________ x $____ = $________________.

        (c)  Total subscription payment (sum of payment amounts on lines (a) and
(b)) = $__________ total payment.*

        METHOD OF PAYMENT (CHECK AND COMPLETE APPROPRIATE BOXES):

	 	[  ]	 	Check, bank draft, or U.S. postal money order payable to
“LaSalle Bank N.A., as Subscription Agent”.
	 
	 	[  ]	 	Wire transfer. If you desire to make payment by wire
transfer, you must contact LaSalle Bank N.A. at (312) __________
to receive a Wire Authorization Form.

        (d)  If the Rights being exercised pursuant to the Basic Subscription
Privilege do not constitute all of the Rights represented by the Subscription
Warrants (check only one):

	 	[  ]	 	Deliver to the undersigned a new Subscription Warrant
evidencing the remaining Rights to which the undersigned is
entitled.
	 
	 	[  ]	 	Do not deliver any new Subscription Warrants to me.

        (e)  [  ] Check here if Rights are being exercised pursuant to the
Notice of Guaranteed Delivery delivered to LaSalle Bank N.A. prior
to the date hereof and complete the following:

	 	 	 
	   	Name(s) of Registered Holder(s)	______________________________________________________________________________

	 	 	 
	   	Window Tick Number (if any)	_______________________________________________________________________________

	 	 	 
	   	Date of Execution of Notice of Guaranteed Delivery	________________________________________________________________

	 	 	 
	   	Name of Institution Which Guaranteed Delivery	___________________________________________________________________

	 	*	 	The maximum number of shares purchasable under the
Oversubscription Privilege is limited to twice the number of shares
purchased under the Basic Subscription Privilege. If the aggregate
subscription payment enclosed or transmitted is insufficient to
purchase the total number of shares included in lines (a) and (b),
or if the number of shares being subscribed for is not specified,
the Rights holder exercising this Subscription Warrant shall be
deemed to have subscribed for the maximum amount of shares that
could be subscribed for upon payment of such amount. If the number
of shares to be subscribed

 

 

	 	 	 	for pursuant to the Oversubscription Privilege is not specified and
the amount enclosed or transmitted exceeds the aggregate
Subscription Price for all shares represented by this Subscription
Warrant (the “Subscription Excess”), the Rights holder exercising
this Subscription Warrant shall be deemed to have exercised the
Oversubscription Privilege to purchase, to the extent available,
that number of whole shares of Common Stock equal to the quotient
obtained by dividing the Subscription Excess by the Subscription
Price, subject to (i) a maximum number of equal to twice the number
of shares purchased under the Basic Subscription Privilege and (ii)
pro-ration, each, as described in the Prospectus. To the extent
any portion of the aggregate Subscription Price enclosed or
transmitted remains after the foregoing procedures, such funds
shall be mailed to the subscriber without interest or deduction as
soon as practicable.

Subscriber’s Signature _____________________________ Telephone No. (___)_________

2

 

FORM 2

(on reverse of Subscription Warrant)

        TO EXERCISE RIGHTS THROUGH YOUR BANK OR BROKER:   Rights represented by
this Subscription Warrant are hereby assigned to (please print in full name and
address and Taxpayer Identification Number or Social Security Number of
transferor):

	 	 	 
	   	Number of Rights being exercised:	______________________________________________________________________________

	 	 	 
	   	Name of beneficial owner and Taxpayer Identification Number or Social Security Number:	_______________________________________

	 	 	 
	   	Address:	_______________________________________________________________________________________________

	 	 	 
	   	Signature(s) of Transferor(s)	_________________________________________________________________________________

	 	 	 
	   	Signatures Guaranteed by:	___________________________________________________________________________________

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