SCR Silicon controlled rectifier. Static Transfer A solid state switching mechanism electronically controlled to pass AC power directly from the utility to an output load. Test connector DB-9 type connector on the LCD panel allowing MGE UPS SYSTEMS Customer Support Service technician to access programmable and diagnostic features of the system. UL Underwriterâs Laboratories, Inc. V Volts VA Volt-amperes, unit for apparent power measurement, equal V x I. VAC Voltage of AC type. Vdc Voltage of DC type. 86-174010-00 B00 Glossary Gâ3