A DC power supply comprising a sealed lead-acid battery, a charging regulator, a discharge pass element, an output power switch for disconnected the power supply from the computer and four light-emitting diode indicators which display the condition and trend of the battery charge state. The power supply...http://www.google.fr/patents/US4595872?utm_source=gb-gplus-shareBrevet US4595872 - Computer-attached uninterruptable DC power supply
