MFJ Enterprises Original MFJ-557 Deluxe Morse Code Practice Oscillator Straight Key w/Volume Control The MFJ-557 Deluxe Morse Code Practice Oscillator runs on a 9 volt battery (not included) or 110 VAC. It measures 8 1/2 x 2 1/4 x 3 3/4 inches. It comes with MFJs famous one year No Matter What warranty.