Various aspects of the present disclosure are directed toward optics and imaging. The training device includes a base unit and a sensory unit. The primary system has a heat exchanger which performs heat exchange between the battery and the cooling water, and a heat exchanger which performs heat exchange between the cooling water and an ambient air. The internal voltage node reaches steady state when the current flowing through the first current source device and first current sink device, whereby the charging or discharging of the voltage at the output voltage node is a function of the timing of the first switching device and second switching device.