The Twin Stim 2nd Edition gives the user the choice of five modes of TENS and two modes of EMS. Features include dual channels seven modes timer patient compliance meter new stronger 100 mA output safety amplitude cover sturdy metal belt clip and rubber side railings for maximum handling. Five TENS Modes: Burst / Normal / Modulation / SD1 / SD2. Two EMS Modes: Synchronous Alternate. System includes device lead wires four self-adhesive reusable electrodes 9-volt battery hard plastic carrying case and instruction manual. Patient compliance meter can store up to 60 sets of operation records and 999 hours. Power Source: 9-volt battery. Pulse Width: 50-300 mS adjustable. Pulse Rate: 2-150 Hz adjustable. Pulse Ramp: 1-8 seconds. Pulse Amplitude: 100 mA peak into 500 phm load. Contraction Time: 2-90 seconds. Relaxation Time: 2-90 seconds. Wave Form: Asymmetrical Bi-Phase Square Pulse. Timer: 1-60 minutes or continuous. One year warranty. Digital 2-channel EMS/TENS unit portable/battery complete