The Stanford Reasearch SIM928 Isolated Voltage Source is ideal for applications where ultra-clean DC voltage is required. Voltage can be set between Tone20 VDC with millivolt resolution, and the source can drive up to Tone10 mA. The output circuit is optically isolated from all earth-referenced charging circuitry, providing maximum flexibility and noise immunity. The system can float to Tone40 V, and the output is short-circuit protected. At the heart of the SIM928 are two independent nickel-metal-hydride rechargeable batteries, each providing up to 12 hours of operation under full load conditions. When a battery is nearly depleted, the SIM928 automatically switches in a second battery. The switchover between batteries is virtually glitch-free, giving you uninterrupted power around the clock. The depleted battery is automatically charged to capacity in about 5 hours. The batteries are guaranteed for 1000 charging cycles, and SRS offers replacement battery sets.