Abstract: A radiation detector is disclosed. The detector comprises: a conversion device configured to develop a voltage when subject to incident radiation; and a switch operable configured to move between a first state and a second state when triggered by a threshold voltage. The conversion device is connected to the switch such that, when the threshold voltage is developed across the conversion device, the switch is triggered to move from the first state to the second state. The detector further comprises an interrogation circuit operable to determine whether the switch is in the first state or the second state, thereby to determine whether the detector has been subjected to a threshold level of radiation associated with the threshold voltage. A system comprising radiation sensitive apparatus and the radiation detector is also disclosed.

Abstract: Method of detecting and tracking an unmanned aerial vehicle, the method comprising, at a detector unit (300a) comprising a first microphone and a second microphone: monitoring for a sound associated with the presence of the unmanned aerial vehicle (505) in the vicinity of the detector unit; in response to the monitoring indicating the presence of the unmanned aerial vehicle, determining, at the detector unit, a phase delay between the sound as received at the first microphone and the sound as received at the second microphone; on the basis of the determined phase delay and a known separation of the first microphone and the second microphone, determining, at the detector unit, an azimuth angle (507a) to the unmanned aerial vehicle from the detector unit; and transmitting, to a computing node (501), the determined azimuth angle for use in determining a location of the unmanned aerial vehicle.