The Twin Stim® Plus is a four channel TENS and EMS combo unit complete with eight electrodes. The Twin Stim® Plus gives the user the choice of three modes of TENS and five modes of EMS. Unit can be powered by four AA batteries or by AC adaptor. Five TENS Modes: Burst / Normal / Modulation / SD1 / SD2. Three EMS Modes: Constant / Synchronous / Alternate. System includes device, AC adaptor, four lead wires, eight self-adhesive. Reusable electrodes, four AA batteries, hard plastic carrying case and instruction manual. Built in patient compliance monitor. Power Source: 4 AA batteries. Pulse Width: 50-300 mS, adjustable. Pulse Rate: 2-150 Hz adjustable. Pulse Ramp: 1-8 seconds. Pulse Amplitude: Adjustable:100 mA peak into 500 ohm load. Contraction Time: 2 - 90 seconds, 1 second/step. Relaxation Time: 0 - 90 seconds, 1 second/step. Wave Form: Asymmetrical Bi-Phasic Square Pulse. Timer: 1-60 minutes or continuous. One year warranty. Digital 4-channel EMS/TENS unit, portable/battery or AC adapter, complete