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                                                                   EXHIBIT 10.21


                           LOAN MODIFICATION AGREEMENT

         This Loan Modification Agreement is entered into as of December 19,
2000, by and between T/R Systems, Inc. (the "Borrower") and Silicon Valley Bank
a California chartered bank doing business in Massachusetts as Silicon Valley
East ("Bank").

1.       DESCRIPTION OF EXISTING INDEBTEDNESS: Among other indebtedness which
may be owing by Borrower to Bank, Borrower is indebted to Bank pursuant to,
among other documents, a Promissory Note and Loan and Security Agreement dated
October 17, 1997, as amended (collectively, the "Loan Agreement"). The Loan
Agreement provided for, among other things, a Committed Revolving Line in the
original principal amount of One Million Dollars ($1,000,000). The Loan
Agreement was modified, pursuant to, among other documents, a Fourth Loan
Modification Agreement pursuant to which, among other things, the Committed
Revolving Line was increased to Three Million Dollars ($3,000,000). Defined
terms used but not otherwise defined herein shall have the same meanings as in
the Loan Agreement.

Hereinafter, all indebtedness owing by Borrower to Bank shall be referred to as
the "Indebtedness."

2.       DESCRIPTION OF COLLATERAL. Repayment of the Indebtedness is secured by
the Collateral as described in the Loan Agreement.

Hereinafter, the above-described security documents and guaranties, together
with all other documents securing repayment of the Indebtedness shall be
referred to as the "Security Documents". Hereinafter, the Security Documents,
together with all other documents evidencing or securing the Indebtedness shall
be referred to as the "Existing Loan Documents".

3.       DESCRIPTION OF CHANGE IN TERMS.

         A.       Modification(s) to Loan Agreement.

                  1.       Subparagraph (f) of Section 6.3 of the Loan Agreement
                           is hereby deleted in its entirety and replaced with
                           the following:

                           "(f) at such times as Advances are outstanding, or
                           prior to an Advance if no Advances are outstanding,
                           within thirty (30) days after the last day of each
                           month, a Borrowing Base Certificate signed by a
                           Responsible Officer in substantially the form of
                           Exhibit C hereto, together with aged listings of
                           accounts receivable."

4.       CONSISTENT CHANGES. The Existing Loan Documents are hereby amended
wherever necessary to reflect the changes described above.

5.       NO DEFENSES OF BORROWER. Borrower (and each guarantor and pledgor
signing below) agrees that, as of the date hereof, it has no defenses against
the obligations to pay any amounts under the Indebtedness.

6.       CONTINUING VALIDITY. Borrower (and each guarantor and pledgor signing
below) understands and agrees that in modifying the existing Indebtedness, Bank
is relying upon Borrower's representations, warranties, and agreements, as set
forth in the Existing Loan Documents. Except as expressly modified pursuant to
this Loan Modification Agreement, the terms of the Existing Loan Documents
remain unchanged and in full force and effect. Bank's agreement to modifications
to the existing Indebtedness pursuant to this Loan Modification Agreement in no
way shall obligate Bank to make any future modifications to the Indebtedness.
Nothing in this Loan Modification Agreement shall constitute a satisfaction of
the Indebtedness. It is the intention of Bank and Borrower to retain as liable
parties all makers and endorsers of Existing Loan Documents, unless the party is
expressly released by Bank in writing. No maker, endorser, or guarantor will be
released by virtue of this Loan Modification Agreement. The terms of this
paragraph apply not only to this Loan Modification Agreement, but also to all
subsequent loan modification agreements.


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         This Loan Modification Agreement is executed as of the date first
written above.

BORROWER:                                    BANK:

T/R SYSTEMS, INC.                            SILICON VALLEY BANK


By: /s/ Lyle W. Newkirk                  By: /s/ Alan P. Spurgin
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Name: Lyle W. Newkirk                      Name: Alan P. Spurgin
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Title: Senior VP/CFO                      Title: Sr. Vice President
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