Constance Brown's Derivative Oscillator was published in her book "Technical Analysis for the Trading Professional".
The oscillator uses a 14-period RSI. The RSI is then double smoothed with exponential moving averages. The default settings for the smoothing periods are 5 and 3.
In a second step a signal line is generated from the smoothed RSI by calculating a simple moving average with a period of 9.
The Derivative Oscillator is calculated as the difference between the smoothed RSI and the signal line and displayed as histogram.
All the values are configurable.