Provided are a method and apparatus for modeling source-drain current of a TFT. The composition dries rapidly, permits further texturing before it dries if desired, is esthetically superior to faux finish top coats made by methods in the prior art, and when dry provides a top coat that is mechanically tough. The entropy accumulator is configurable for accumulating entropy of the input sequence and providing a binary random output sequence based on the accumulated entropy. In some aspects, beacon transmit power may be set based on a defined outage radius parameter and the total received signal power on a channel. The calibration timing circuit is like the timing circuits of the micro-mirror cells.