nRF51 Low power modes and power profiles documentation The low power modes for the nRF51 series are System On and System Off. You can read about them in the nRF51 Series Reference Manual v3.0 sections 12.1.5 and 12.1.7. Additional information are also given here. If you are using ANT or BLE softdevice for the nRF51, look at the "Power Profiles" chapter in the Softdevice Specification document for