Mine Rescue Field Exam From the 2013 Ohio Valley Mine Rescue Contest, Cadiz, OH Progress Indicator: Question 2 of 10 2.  Medium Voltage is defined as: Choices: Voltage from 600 to 1,000 volts Voltage from 661 to 1,000 volts Voltage from 551 to 1,000 volts Voltage from 676 to 1,000 volts