Similar to 'Delta Trace', used to view changes in the RF spectrum compared to a user-supplied 'Reference' trace. Plotting the data in this way makes it easy to detect RF changes that differ from the Reference trace.
When scanning begins, the Reference trace appears as the stationary, background gray trace. For all subsequent scans, the Reference trace is subtracted from the current trace and the difference, i.e. ‘delta’, is displayed as red and green bars -- a red bar means the current signal strength at that frequency is less than the reference, and a green bar means the current signal strength at that frequency is greater than the reference. Plotting the data in this way makes it easy to detect RF changes in transmitted signals that occurred since the initial snapshot and is most useful in environments where RF transmissions change over time.