The SI-200 is a high voltage, isolated stimulator designed to deliver safe, transcutaneous stimulus pulses to a nerve or a muscle being studied. The design of the SI-200 permits the desired current of the stimulus pulse to be generated despite the impedance on the path that the current follows. The SI-200 adjusts the voltage needed to maintain that current automatically by increasing the voltage that drives the current up to a maximum of 150 volts. Because of this capability, the SI-200 is categorized as a constant current stimulator. However, the current output of the SI-200 is limited to a maximum of 20 milliamperes, with a maximum duration of 10 milliseconds and a maximum frequency of 50Hz.
