The MFJ-557 Deluxe Morse Code Practice Oscillator features a Morse Code straight key on a non-skid heavy steel base -- it stays put on the table and doesn't move around while you're sending. The MFJ-557 lets you practice sending code at home, work, riding in your car -- practically anywhere -- because it's so easy to take it wherever you go. Volume control adjusts from barely audible to blaring full sound. You can practice without bothering anyone. Tone control gives you a wide adjustment from high "squeaky" to low "booming" tones. You even get an earphone jack for private listening. You can plug in an external speaker for super high volume in the classroom. When you're finished cleaning up your sloppy fist with the MFJ-557, hook up the straight key to your transmitter and go on-the-air sounding like you were born working QSOs. Don't pass up this super CW buy! The MFJ-557 also has a built-in speaker and adjustable contacts. The MFJ-557 Deluxe Morse Code Practice Oscillator runs on a 9-volt battery (not included) or 240 VAC PSU with 9volt output,. It measures 8 1/2 x 2 1/4 x 3 3/4 inches.