output to the scu processor for processing processing is achieved by a mini computer such as a cdc model 469 mini computer which is programed to perform a processing algorithm that essentially develops a background value in terms of the mean and standard deviation for a specified number of sweeps of the search head the input to the control panel from the processor is a signal level which is related to the magnitude of the processing data algorithm the background value is continuously updated during each sweep by the processor and the signal received from the receiver is compared against this background value a received signal outside the threshold level of variance from the mean will indicate the presence of a buried object and will trigger the second or pinpoint mode when the second mode is triggered a signal from the scu processor sets off an indicator signal on the control panel to indicate the shift in mode and transmits an anolog input to the pinpoint generator as well as a shift command to the search pinpoint selector which stops the metronome signal and feeds the signal from the pinpoint generator to the audio output the analog input is developed by a comparison between the stored background value and the received signal and is converted by the pinpoint generator into a signal that produces a geiger type.