The envelope detection circuit was implemented using passive and active analog devices. The comparison circuit was implemented with a Motorola 6811 microcontroller. The envelope detector, tuned to a frequency average for human speech, outputs a pattern generally outlining the amplitude variation in it's input. The output roughly consists of pulses of different lengths and heights. This output signal is sampled by the microcontroller where the pulses are measured and stored, characterized by two parameters, length and height.
Length can be either short or long, and height can be either short or tall.
Once an entire spoken command, consisting of several of these pulses, is interpreted, it can be compared to a database of known pulse patterns to determine which command was spoken.