(2) SMD OM-1 LED Sound System Output Monitors - Double Play Combo Pack Operating Voltage: 8v-22v - Constant LED current and brightness regardless of battery voltage (wont dim with your beat) Adjustable Input Sensitivity, Input Reading Range - 10Vac - 150Vac RMS (200Vac Maximum) Accuracy: +/- 0.20 Volts (due to the nature of a bar graph) 100% Analog circuitry allows for near instantaneous voltage accuracy versus a traditional digital voltage meter Mil spec FR4 circuit board, Regulated Power Supply