1. A supervisory circuit for deriving a parametric output of an input signal comprising: a) input means for receiving said input signal; b) mean square processor for determining the mean square value of the input of said input signal; c) conversion processor for converting said mean square value into a random pulse density modulated bitstream representative of said mean square value; d) stochastic processor for converting said random pulse density modulated bitstream into a stochastic representation of the RMS value of the input signal; e) output means for outputting said stochastic representation of said RMS value.