EXHIBIT 10.12 PROMISSORY NOTE EXTENSION The undersigned, The Holding Company, being the holder of a promissory note (the "Note") from Logic Devices Incorporated dated February 24, 1999 in the principal amount of $150,000, hereby agrees to the extension of the Maturity Date, as defined in the Note, to November 30, 1999. September 30, 1999 The Holding Company By: /s/ Burton W. Kanter -------------------------- Burton W. Kanter President 39