The keys are pressed one by one until the user observes {HEAD ~ the desired effect} on {TAIL ~ the remotely controlled device} 
The keys are pressed one by one until the user observes { HEAD ~ the desired effect } on { TAIL ~ the remotely controlled device }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL