Set the sensitivity level by pressing the L/M/H button. Low (L), medium (M), or high (H) sensitivity will be indicated by the respective LEDs. The higher the concentration of refrigerant in the ambient air, the lower the sensitivity setting should be to minimize false trips. The TURBO function is an additional 4th sensitivity that pushes the SRL2 to it highest possible sensitivity. This feature is activated by pressing the PEAK button four times in succession, and can only be activated while on the high(H) sensitivity level. The TURBO function is an additional 4th sensitivity that pushes the SCL2 to it highest possible sensitivity. This feature is activated by pressing the PEAK button four times in succession, and can only be activated while on the high(H) sensitivity level.