<PAGE>
 
                                                                   Exhibit 10.44

                   REVOLVING LINE-OF-CREDIT PROMISSORY NOTE
                   ----------------------------------------

DATE:   As of August 1, 1997.

PROMISE TO PAY:   Borrower, for value received, promises to pay to the order of
Lender the principal amount of, and all interest accruing under, this note in
accordance with the provisions of this note.

PRINCIPAL AMOUNT: Up to One Million Three Hundred Thousand and No/100th Dollars
($1,300,000.00).

LENDER:   SouthTrust Bank, National Association, a national banking association,
and its successors and assigns.

BORROWER: La-Man Corporation, a Nevada corporation.

GUARANTORS:  Don Bell Industries, Inc., a Florida corporation; Don Bell
Industries of Nevada, Inc., a Nevada corporation; Nevada SEMCO, Inc., a Nevada
corporation; J. M. Stewart, Corporation, a Florida corporation; J. M. Stewart
Industries, Inc., a Florida corporation; Certified Maintenance Service, Inc., a
Florida corporation; and Vision Trust Marketing, Inc., a Florida corporation;
all jointly and severally.

INTEREST:   Interest shall accrue under this note on the unpaid principal
balance at a per annum rate equal to, and shall be adjusted daily as necessary
to equal, the base rate of SouthTrust Bank, National Association (the "Lender"),
in effect from time to time, as determined in the sole discretion of the Lender,
plus 100 basis points (1.00%).  The base rate is not necessarily the lowest rate
charged by the Lender.  The base rate is the fluctuating rate of interest
established by the Lender from time to time as an index or rate which may or may
not at any time be the best or lowest rate charged by the Lender on any loan.
Any interest rate based on a fluctuating index or base rate will, unless
otherwise provided, change each time and as of the date that the index or base
rate changes.  The base rate as defined herein on the date of this note is 8.50%
and the interest rate applicable to this note as of the effective date of this
note is 9.50% per annum.

COMPUTATION OF INTEREST:  Interest will be computed on the balance of principal
remaining unpaid from time to time on the basis of the actual number of days
elapsed in a year composed of 365 or 366 days, as the case may be.

REVOLVING NOTE:  This is a revolving note evidencing the borrowings up to the
principal sum shown above, but notwithstanding such expression, the actual
indebtedness from time to time evidenced hereby shall be the sum of all advances
by the Lender to the Borrower hereunder, less the aggregate amount of all
principal payments made under this revolving note by the Borrower to the Lender,
it being the intent hereof and the purpose of this revolving note to provide a
revolving line of credit which the Borrower may draw against and which the
Lender will advance 
<PAGE>
 
                                                                   Exhibit 10.44

from time to time and which the Borrower may repay in whole or in part from time
to time and again draw against, provided that the principal amount outstanding
under this revolving note shall not at any time exceed the principal sum shown
above.

PRINCIPAL DISBURSEMENTS / MAINTENANCE OF LOAN-TO-VALUE PERCENTAGES:  The
Borrower agrees that the disbursement of principal under this note, and the
outstanding principal balance existing from time-to-time hereunder, are
conditioned upon the maintenance of certain values relating to the Borrower's
Collateral (the capitalized terms "Collateral", "Accounts Receivable", and
"Inventory" used in this paragraph and its subparts shall have the same meanings
ascribed to them in the Mortgage and Security Agreement of even effective date
which secures payment of this note).  The terms "eligible Accounts Receivable"
shall mean the Borrower's Accounts Receivable aged 90 days or less, but
excluding therefrom any Account Receivable that comprises more than 50% of the
total of all Accounts Receivable.  Based upon the values so determined for
eligible Accounts Receivable and Inventory, the outstanding principal balance of
this note shall not exceed:

     (a). Eighty percent (80%) of the fair market value of the eligible Accounts
Receivable; plus

     (b). Fifty percent (50%) of the fair market value of the Inventory that is
considered readily salable (but in no event for purposes of this calculation
shall the Inventory be valued in excess of $1,000,000); or

     (c). One million three hundred thousand dollars ($1,300,000.00);

whichever shall be the lesser sum.

A borrowing base certificate executed by the Borrower's chief financial officer
in form and content satisfactory to the Lender shall be provided to the Lender
no less frequently than monthly.  In the event the eligible Accounts Receivable
and/or Inventory decline in value and the loan-to-value percentages set forth
above are exceeded, then and under such circumstances the Borrower shall, within
5 days from written notice from the Lender to the Borrower, reduce the
outstanding principal balance by the sum necessary to attain, and thereafter
maintain, the loan-to-value percentages set forth above.

GOVERNMENTAL IMPOSITIONS:   In the event state documentary stamp taxes,
intangible taxes or other governmental impositions in excess of those required
to be paid upon the full amount of this revolving note or any documents
evidencing a lien to secure this revolving note are deemed to be owed to any
governmental authority, the Borrower agrees to pay the same and hold the Lender
harmless from and against any and all of the costs involved in paying the
additional taxes and any penalties or interest required to be paid thereon.  If
the Lender is required to pay the same, the Borrower agrees to immediately repay
the Lender upon demand the full amount 

                                    Page 2
<PAGE>
 
                                                                   Exhibit 10.44

paid by the Lender to any governmental authority as additional taxes, penalties,
costs and/or interest. Any sum so paid by the Lender under this paragraph shall
be added to the principal indebtedness owed under this note and shall accrue
interest at the highest lawful rate until paid.

PAYMENTS: Principal and interest are payable as follows:

     (a). Interest only shall be payable in monthly installments commencing
October 1, 1997, and continuing on the same day of each month thereafter; and

     (b). Unless the term of this note is extended as provided in subparagraph
(c) below, the entire unpaid principal balance and all accrued and unpaid
interest shall be due and payable in full on October 1, 1999.

     (c). Commencing on or about October 1, 1998 and continuing on or about
October 1 of each year thereafter during the term of this note or any extension
thereof, the Lender shall conduct an annual review of the Borrower's overall
financial condition and economic performance, its compliance with the terms,
covenants, and obligations of this note and the instruments that secure payment
of this note, and such other matters as the Lender, in its sole discretion,
shall consider pertinent to its review and analysis of the loan evidenced by
this note.  If the Lender in its sole discretion is satisfied with the results
of its review, it shall notify the Borrower in writing of its approval within 10
days after October 1 of each year this note remains outstanding, and the term of
this note shall then be extended for an additional period of two years from
October 1 of each year the Lender favorably approves the annual review.  In the
event the Lender does not elect in its sole discretion to extend the term of
this note after any annual review as provided above, it shall notify the
Borrower in writing of its decision within 10 days after October 1 of the year
in which its decision not to extend the term of this note is made.  Notices from
the Lender to the Borrower shall be given in writing and delivered personally or
sent by United States Certified Mail to the then current address of the Borrower
as set forth in the Lender's records.

APPLICATION OF PAYMENTS:  The Borrower has established a controlled
disbursement account with the Lender, and all advances, payments, and repayments
hereunder will be made in accordance with the terms and conditions of said
controlled disbursement account.

PLACE OF PAYMENT:  All payments required to be made under this note and any
instrument securing this note will be made at 100 East New York Avenue, DeLand,
Florida 32724, or at such other place that Lender may designate in writing.

INTEREST RATE AFTER MATURITY:  After the maturity of this note, whether by
acceleration or in due course, all unpaid principal will bear interest at the
then highest lawful rate.

                                    Page 3
<PAGE>
 
                                                                   Exhibit 10.44

MAXIMUM INTEREST:  The total amount or rate of interest payable under this note
in any one year, or for any other period of time for which interest rates are
required to be calculated for the purpose of determining compliance with any
applicable laws governing the maximum amount or rate of interest that may be
charged or collected under this note, will not exceed that highest amount or
rate of interest that is legally permitted.  In the event that interest in
excess of the highest lawful amount is paid or collected for any such period of
time, the amount of such excess, upon discovery of same, will be applied on the
unpaid principal balance of this note as of the time of such overpayment or
collection or, if required by law, will be refunded, and the interest will be
recomputed so as not to exceed the highest lawful rate.

LATE CHARGE:  If all or any portion of any payment of principal or interest due
under this note is not received by the Lender within ten (10) days following its
due date, a late charge equal to five percent (5%) of the overdue amount will
become immediately due and payable without notice.

DEFAULT:  If any monetary obligation under this note or any instrument securing
payment of this note is not paid within 10 days after it is due, this note will
mature and all principal and accrued interest remaining unpaid will become
immediately due and payable, at the option of Lender, after written notice of
default to any obligor.  If any non-monetary duty or obligation under this note
or any instrument securing this note is not performed or completed and a
condition of default exists as a result thereof which remains uncured after 30
days notice (or such longer cure period as the Lender may in its reasonable
discretion grant if the non-monetary condition of default is not, with the
exercise of utmost due diligence, completely correctable within said 30 days) to
any obligor under this note to cure the same, this note will mature and all
principal and accrued interest remaining unpaid will become immediately due and
payable without further notice, at the option of Lender.  Failure to exercise
the option to accelerate will not constitute a waiver of the right to exercise
the same in the event of any subsequent default.  Notice required from the
Lender to any obligor concerning any non-monetary default under this note or any
instrument securing this note shall be sufficient if delivered directly, sent by
United States Certified Mail with return receipt requested, or sent by express
receipted courier service to the last known address of the obligor as shown on
the records of the Lender.

SECURITY; CROSS-DEFAULT:  This note is secured by a mortgage and security
agreement, and a collateral assignment of rents and leases.  All instruments
securing this note are cross-defaulted with one another and with this note.  At
the option of Lender, a default under any such instrument will constitute a
default under this note and vice versa.

RIGHT OF PREPAYMENT:  Prepayment of the principal amount of this note or any
unpaid principal balance may be made in full or in part at any time without
penalty.  All unpaid accrued interest must be paid simultaneously as a condition
to such right of prepayment.

                                    Page 4
<PAGE>
 
                                                                   Exhibit 10.44

ENFORCEMENT AND COLLECTION EXPENSES.  All persons obligated under this note in
any capacity shall pay or reimburse the Lender for all costs, professional fees,
and expenses, including attorney's fees, reasonably incurred by Lender, whether
or not legal action is instituted, with respect to collection of the
indebtedness secured hereby, the enforcement of Lender's rights hereunder, or
incurred by the Lender in any proceeding in which the Lender is made a party or
participant, including but not limited to such fees, expenses, and costs
incurred in any phase of litigation in the trial court or on appeal, and all
matters and appearances connected with any trial, retrial, hearing, rehearing,
appeal, mediation, arbitration, condemnation proceeding, bankruptcy case,
bankruptcy proceeding or matter, administrative proceeding, criminal or civil
forfeiture, lien enforcement or foreclosure proceedings.  All of such costs,
fees and expenses shall be secured by the lien of all instruments securing
payment of this note, shall bear interest at the maximum rate set forth in this
note, and, at the option of the Lender, shall be payable upon demand.

JOINT AND SEVERAL LIABILITY:  All persons liable on this note as makers,
endorsers, guarantors, or in any capacity are jointly and severally liable for
all obligations represented by or arising under this note and all instruments,
if any, securing payment of this note.

WAIVERS:  Each person obligated under this note in any capacity waives
presentment, demand, protest, notice of protest, dishonor, notice of maturity
and notice of non-payment on maturity.

DELIVERY:  This note is made and delivered in Volusia County, Florida.

FINANCIAL STATEMENTS:  The term "GAAP" shall mean generally accepted accounting
principles applied on a consistent basis throughout the periods involved.  The
Borrower, and each Guarantor whose assets form any part of the Collateral that
secures payment of this note, agree to furnish periodic updated financial
statements in such form or detail as reasonably required by Lender without
expense to the Lender, as follows:

     (a). Monthly:    Within 30 days after the end of each calendar month, the
Borrower shall provide the Lender with a complete and accurate listing and
summary aging report of all accounts receivable, an inventory report in summary
form coinciding in substance with the Borrower's internally prepared
consolidated financial statements as of the last day of the month then ended,
and a monthly borrowing base certificate; and

     (b). Quarterly:  Within 45 days after the close of each fiscal quarter, the
Borrower shall provide the Lender with a true copy of the Borrower's Form 10-QSB
Report (or Form 10-Q, if applicable) as filed with the Securities and Exchange
Commission, or in the event the Borrower is not required to file such Report or
the information described below is not included therein, such comparable
consolidated 

                                    Page 5
<PAGE>
 
                                                                   Exhibit 10.44

financial statements of the Borrower and its subsidiaries (including the
Guarantors) including a complete and accurate listing and summary aging report
of all accounts receivable, an inventory report in summary form coinciding in
substance with the Borrower's internally prepared financial statements as of the
last day of the quarter then ended, and financial statements of the Borrower
consisting of balance sheets and operating statements and a listing of all
contingent liabilities of the Borrower for the period involved and such other
statements as Lender may reasonably request. The quarterly financial information
required hereby may be unaudited and need not include all information and
disclosures required by GAAP; however, such information will reflect all
adjustments (consisting solely of normal recurring adjustments) which are, in
the opinion of the Borrower's management, necessary for a fair presentation of
the consolidated financial position and results from operations of the Borrower
and its subsidiaries for such quarterly periods. All of such interim financial
statements shall be taken from the books and records of the Borrower, and
certified by the chief financial officer of the Borrower as fairly presenting in
all material respects the consolidated financial position of the Borrower and
its subsidiaries as of the date thereof and the results of their operations and
their cash flows for the periods covered thereby. At the time of furnishing such
financial statements, the Borrower shall furnish the Lender with a certificate
from the President or chief financial officer of the Borrower stating that he
has reviewed the requirements of this note and the affairs of the Borrower and
that to the best of his knowledge and belief he is unaware of the occurrence of
an event which constitutes a default hereunder or which would constitute such a
default with the giving of notice or the lapse of time or both, and if so,
stating the facts with respect thereto.

     (c). Annual:  Within 90 days after the close of each fiscal year, the
Borrower shall furnish the Lender with a true copy of the Borrower's Form 10-KSB
Annual Report (or Form 10-K, if applicable) as filed with the Securities and
Exchange Commission, but in the event the Borrower is not required to file such
Annual Report, such comparable audited consolidated financial statements of the
Borrower and its subsidiaries (including the Guarantors) audited by certified
public accountants acceptable to the Lender and certified as fairly presenting
in all material respects the consolidated financial position of the Borrower and
its subsidiaries as of the date thereof and the results of their operations and
their cash flows for the periods covered thereby, in accordance with GAAP. In
addition, the Borrower shall provide all internal notes and back-up
documentation relating to the consolidation of the financial statements of the
Borrower and its subsidiaries, including the Guarantors. At the time of
furnishing said financial statements, the Borrower shall furnish Lender with a
certificate from the President and the chief financial officer of the Borrower
stating that they have reviewed the requirements of this note and the affairs of
the Borrower and that to the best of their knowledge and belief they are unaware
of the occurrence of an event which constitutes a default hereunder or which
would constitute such a default with the giving of notice or the lapse of time
or both, and, if so, stating the facts with respect thereto.

                                    Page 6
<PAGE>
 
                                                                   Exhibit 10.44

     (d). Inventory Audit: If requested by the Lender and upon reasonable
advance notice, the Borrower shall make its books, records, and inventory
available to the Lender (or its designee) for inspection and audit at the
Lender's sole cost and expense. Any such audit shall be conducted without undue
disruption of Borrower's business operations, and not more frequently than
annually.

In the event the documents described in this paragraph are not provided to the
Lender within the time provided herein, for a period beginning 10 days after
written notice of such default and ending upon the curing of said noticed
default, the interest rate provided in this note may (at the Lender's option
without accelerating the balance due) increase to a rate equal to 3% above the
Lender's base rate of interest.  The base rate is not necessarily the lowest
rate charged by the Lender.  The base rate is the fluctuating rate of interest
established by the Lender from time to time as an index or rate which may or may
not at any time be the best or lowest rate charged by the Lender on any loan.
Any interest rate based on a fluctuating index or base rate will change each
time and as of the date that the index or base rate changes.

AFFIRMATIVE COVENANTS OF BORROWER:  The Borrower covenants and agrees that from
the date hereof, and during any extension of the term hereof, until payment in
full of all principal and interest due under this note, unless the Lender shall
otherwise consent in writing, the Borrower shall:

     (a). Conduct its business in the ordinary course and in substantially the
same manner and in substantially the same areas as such business is now and
heretofore has been carried on and conducted; and

     (b). Comply fully with all applicable statutes, laws and regulations,
maintain the corporate existence of the Borrower and each subsidiary, if any,
and shall maintain, preserve and keep its properties and assets in good repair,
working order and condition (reasonable wear and tear, excepted), making all
needed replacements, additions, improvements and renewals thereto as are
reasonably required to carry on its business; and

     (c). Maintain the following financial covenants in accordance with the
definitions set forth below:

          (i). Debt to tangible net worth:  The ratio of total liabilities (less
debt subordinated to the Lender) to tangible net worth (plus debt subordinated
to the Lender) which shall not exceed 3.10 to 1.00 during fiscal year 1998; 2.70
to 1.00 during fiscal year 1999; and 2.40 to 1.00 during fiscal year 2000 and
thereafter.  "Tangible net worth" is defined as total assets minus total
liabilities minus any intangible assets as defined by GAAP, such as, but not
limited to, the book value of any patents, trademarks, trade-names, copyrights,
non-compete agreements, franchises, or experimental expenses or goodwill or
other amounts representing the excess of the purchase price of assets or stock
over the value assigned to them on the books of the Borrower.

                                    Page 7
<PAGE>
 
                                                                   Exhibit 10.44

          (ii).  Consolidated working capital:  "Consolidated working capital"
is defined as current assets minus current liabilities, and must equal or exceed
$750,000 during fiscal year 1998, equal or exceed $1,000,000 during fiscal year
1999, and equal or exceed $1,250,000 during fiscal year 2000 and thereafter.
"Current assets" is defined as the amount at which all of the current assets of
the Borrower (and its subsidiaries, including the Guarantors) would be properly
classified as current assets shown on a consolidated balance sheet at such date
in accordance with GAAP. "Current liabilities" is defined as the amount at which
all of the current liabilities of the Borrower (and its subsidiaries, including
the Guarantors) would be properly classified as current liabilities on a
consolidated balance sheet at such date in accordance with GAAP.

          (iii). Current ratio:  Maintain at all times a current ratio
("current ratio" being defined as the quotient of current assets divided by
current liabilities) of 1.25 to 1.00; and

          (iv).  Fixed charge coverage:  "Fixed charge coverage" is defined as a
fraction in which the numerator is the sum of the net income of the Borrower and
its subsidiaries, including the Guarantors, (after provision for federal and
state taxes) at the close of the Borrower's fiscal year, plus the interest,
lease, and rental expenses of Borrower for said period, plus the sum of non-cash
expenses or allowances for such period (including amortization or write-down of
intangible assets, the net addition or net decrease in the loan loss reserves
for customer accounts, depreciation, depletion, and deferred taxes and expenses)
and the denominator is the sum of the current portion of the long term debt of
the Borrower and its subsidiaries, including the Guarantors, as of the
applicable date, plus the interest, lease, and rental expenses for the said
period preceding the applicable date.  The fixed charge coverage must be
maintained at not less than 1.30 at all times during the term of this note or
any extension thereof; and

          (v).   Dividends and withdrawals:  Dividends and withdrawals are
allowable to the extent they do not result in the violation of the financial
covenants of this note; and

          (vi).  Additional debt:  The Borrower shall not create, incur, assume
or suffer to exist any debt or obligation for money borrowed, or guarantee, or
endorse, or otherwise be or become contingently liable in connection with the
obligations of any person (including, without limitation, any subsidiary or
Guarantor) in excess of $50,000.00 annually, without the written consent of the
Lender.  Any purchases of equipment that create a purchase money security
interest are exempt from this covenant.

CONTINUING DEPOSITOR RELATIONSHIP:  The interest rate charged by the Lender in
this note is predicated upon a total continuing depositor relationship with the
Borrower, satisfactory to the Lender, during the term of this note.

                                    Page 8
<PAGE>
 
                                                                   Exhibit 10.44

NUMBER AND GENDER:  Whenever the singular number is used in this note, the same
shall include the plural, and vice versa, and the neuter gender shall include
both the masculine and feminine genders.

SIGNED, SEALED, AND DELIVERED at Daytona Beach, Volusia County, Florida as of
the date and year first above written.

LA-MAN CORPORATION


By: /s/ J. William Brandner
   -------------------------------------
J. William Brandner, Its President

Documentary Stamps Have Been Affixed To The Original Mortgage And Cancelled.

                              CORPORATE GUARANTY
                              ------------------

     In consideration of the extension of credit evidenced by the foregoing
note, the undersigned jointly and severally hereby absolutely, irrevocably and
unconditionally guarantee payment of all principal and interest under the note
to the Lender. The liability of the undersigned shall not be partially or wholly
released by reason of any extension of time for payment, renewal, modification,
delay, waiver, surrender or release of the note, addition or release of co-
makers, endorsers, guarantors, or sureties, institution of any suit, or the
obtaining of any judgment against any party primarily or secondarily liable on
the note; and the undersigned expressly waives demand, protest, notice of
acceptance of this guaranty and notice of actions taken pursuant hereto. The
undersigned agree to be bound by all of the terms and covenants of the note,
including but not limited to all rights and remedies of the Lender. In case of
default in payment of the note, legal action may be taken by the Lender against
any one or more of the undersigned corporations regardless of whether such
action has been commenced against the maker. In any such action, any party
obligated under the note in any capacity may be joined as a party defendant at
the option of the Lender.

Dated as of August 1, 1997.

Don Bell Industries, Inc.                   Don Bell Industries of Nevada, Inc.


By: /s/ J. William Brandner                 By: /s/ J. William Brandner
   ------------------------------------        ---------------------------------
J. William Brandner, Its Vice President     J. William Brandner, Its Vice 
as Corporate Guarantor                      President as Corporate Guarantor  
                                            

                                    Page 9
<PAGE>
 
                                                                   Exhibit 10.44

Nevada SEMCO, Inc.                           J. M. Stewart, Corporation


By: /s/ J. William Brandner                  By: /s/ J. William Brandner
   ------------------------------------      ---------------------------------
J. William Brandner, Its Vice President      J. William Brandner, Its Vice 
as Corporate Guarantor                       President as Corporate Guarantor  
                                             

J. M. Stewart Industries, Inc.               Certified Maintenance Service, Inc.


By: /s/ J. William Brandner                  By: /s/ J. William Brandner
   ------------------------------------      ---------------------------------
J. William Brandner, Its Vice President      J. William Brandner, Its Vice 
as Corporate Guarantor                       President as Corporate Guarantor  
                                             

Vision Trust Marketing, Inc.


By: /s/ J. William Brandner             
   ------------------------------------ 
J. William Brandner, Its President 
as Corporate Guarantor                  

                                    Page 10