EXHIBIT 10.13 PROMISSORY NOTE EXTENSION The undersigned, William J. Volz, being the holder of a promissory note (the "Note") from Logic Devices Incorporated dated February 24, 1999 in the principal amount of $100,000, hereby agrees to the extension of the Maturity Date, as defined in the Note, to December 31, 1999. September 30, 1999 /s/ William J. Volz ----------------------- William J. Volz 40