<PAGE>   1
                                                                   EXHIBIT 10.40

                            SECURED PROMISSORY NOTE




$335,887.94                                                Date:  March 27, 1998

                                                           Due:   April 1, 2001


FOR VALUE RECEIVED, MachOne Communications, Inc. a California corporation (the
"Borrower") hereby promises to pay to the order of Comdisco, Inc., a Delaware
corporation (the "Lender") at P.O. Box 91744, Chicago, IL 60693 or such other
place of payment as the holder of this Secured Promissory Note (this "Note") may
specify from time to time in writing, in lawful money of the United States of
America, the principal amount of THREE HUNDRED THIRTY-FIVE THOUSAND EIGHT
HUNDRED EIGHTY-SEVEN and 94/100 Dollars ($335,887.94) together with interest at
eight percent (8.0%) per annum from the date of this Note to maturity of each
installment on the principal hereof remaining from time to time unpaid, such
principal and interest to be paid in 36 equal monthly installments of $10,534.80
each, commencing May 1, 1998 and on the same day of each month thereafter to and
including April 1, 2001 and an additional final installment of $50,383.19
("Balloon Payment") to be paid on April 1, 2001, such installments to be applied
first to accrued and unpaid interest and the balance to unpaid principal.
Interest shall be computed on the basis of a year consisting of twelve months of
thirty days each.

This Note is the Note referred to in, and is executed and delivered in
connection with, that certain Loan and Security Agreement of even date herewith
by and between Borrower and Lender (as the same may from time to time be
amended, modified or supplemented in accordance with its terms, the "Loan
Agreement"), and is entitled to the benefit and security of the Loan Agreement
and the other Loan Documents (as defined in the Loan Agreement), to which
reference is made for a statement of all of the terms and conditions thereof.
All terms defined in the Loan Agreement shall have the same definitions when
used herein, unless otherwise defined herein.

The Borrower waives presentment and demand for payment, notice of dishonor,
protest and notice of protest and any other notice as permitted under the UCC or
any applicable law.





                                      -1-
<PAGE>   2
This Note has been negotiated and delivered to Lender and is payable in the
State of Illinois, and shall not become effective until accepted by Lender in
the State of Illinois. This Note shall be governed by and construed and enforced
in accordance with, the laws of the State of Illinois, excluding any conflicts
of law rules or principles that would cause the application of the laws of any
other jurisdiction.

       BORROWER:                   MACHONE COMMUNICATIONS, INC.
                                   992 S. DE ANZA BLVD.
                                   SAN JOSE, CA 95129

                                   Signature:   /s/ [Signature Illegible]
                                             -------------------------------

                                   Print Name:  [Illegible}
                                             -------------------------------

                                   Title:       Secretary
                                             -------------------------------






                                      -2-