Methods for operating a control circuit, having a programmable signal characteristic, in a manner so as to gradually vary a D.C. analog output level from an initial value to a final value, as well as for abrupt changes therein, when an isolation-and-rectification network is used to recover a D.C. voltage...http://www.google.com.au/patents/US4484295?utm_source=gb-gplus-sharePatent US4484295 - Control circuit and method for varying the output of a waveform generator to gradually or rapidly vary a control signal from an initial value to a desired value
