The disclosure relates to a device and a method for validating documents of value, especially a low power validator for validating documents of value is described comprising: a processing unit for controlling operation of the validator; an inlet for receiving a document of value from a user; and a power management system for transitioning the validator between a power conserving mode and a normal operating mode, wherein the power management system comprises a wake up unit arranged to monitor the inlet for the presence of a document of value and to monitor the voltage provided from a power source.