The Model 942A UDR, when connected to a Model 943 Series Scintillation Detector, comprises a monitoring system which operates over a seven decade range. The UDR provides display, control, and annunciation functions for the monitoring system, and will display readings in the range of 10 to 107 CPM. Standard features for the instrument consist of a five digit display of the radiation value and a multicolored bargraph indicator which covers the entire range of the UDR. The bargraph will change color in the event of an alarm condition (green for normal, amber for warning and red for high). Front panel alarm indicators and rear panel relay outputs for alarm annunciation are also included. Front panel pushbuttons are provided to apply power, display alarm limit set points, acknowledge alarms, and activate the check source. Analog outputs of 0 to 10 VDC (1) and 4 to 20 mA (2) are provided for recording and computer monitoring. The outputs may also be used to drive a remote meter or a local (i.e. near the detector) indicator. All electronics required to interface with a Model 943 Series detector are included within the Model 942A UDR. The electronics consist of a high voltage power supply, low voltage DC power supply and the hardware/software required for UDR operation. The system also includes an overrange indicator to preclude the possibility of on-scale readings when the radiation field is beyond the range of the detector.