Dual Channel 4000 MHz Unit comes complete with set of 2 wires pack of 4 silver/silver chloride self-sticking electrodes 9V alkaline battery ac adaptor instruction book and attractive carry case. Dual channel - quadra polar Adjustable pulse amplitude Carrier frequency plus interference frequency Sweep and treatment timers. Shipping Carton Size: 12 L x 10 W x 6 H HCPCS Suggested Code: E0730 Interferential stimulators use a fixed carrier frequency of 4 000 Hz per second and also a second adjustable frequency of 4 001-4 400 Hz per second. When the fixed and adjustable frequencies combine (heterodyne) they produce the desired signal frequency (Interference frequency)