This is a versatile code practice oscillator that can be used with K1EL keyers or just about any keyer on the market. True sine wave output with adjustable frequency and volume. A connector is provided to drive an external speaker or headphones with plenty of clean output. RCA jack outputs on back with external power and speaker/headphone connector. Exclusive KeyerSync allows you to chain several CPOs together to simulate two way or net operations. You hear what you are sending along with everyone else on the simple two wire network. This is a bare bones kit, we supply the board and all components, you supply an enclosure, power supply and speaker.