1. A method to identify a spoken command comprising voiced and unvoiced intervals in a particular order, and to responsively select an action from a set of predetermined actions, said method comprising the steps: 3.1 Converting sound of the spoken command into a digital signal comprising periodic digital measurements of the sound using a transducer and a converter; 3.2 Analyzing the digital signal to detect slow variations therein, by deriving an integrated signal by additively combining successive digital measurements, and comparing the integrated signal to a slow-variation threshold, a slow variation being detected when the integrated signal exceeds the slow-variation threshold; 3.3 Analyzing the digital signal to detect fast variations therein, by deriving a differentiated signal by subtractively combining successive digital measurements, and comparing the differentiated signal to a fast-variation threshold, a fast variation being detected when the differentiated signal exceeds the fast-variation threshold; 3.4 Analyzing the slow variations to detect voiced intervals having voiced sound, and analyzing the fast variations to detect unvoiced intervals having unvoiced sound; 3.5 Preparing a command sequence indicating the order of voiced and unvoiced intervals in the spoken command; 3.6 Comparing the command sequence to templates that indicate the order of voiced and unvoiced intervals in acceptable commands using a computer, each template being associated with one action in the set of predetermined actions; 3.7 And, when the command matches one of the templates, selecting the action associated with the matched template.