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)