The pilot of the retractable landing gear-equipped airplane reported that, during approach the green landing gear extended light was illuminated. He further reported that "it [was] possible that [he] inadvertently cycled the landing gear back to a gear up position". The airplane landed gear up and was destroyed by a postaccident fire. During a telephone interview with a National Transportation Safety Board investigator, the pilot reported that the landing gear handle and the trim wheel were next to each other and it is probable that when operating the trim wheel, he moved the landing gear handle. He added that that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. A friend of the pilot reported that the pilot used a LightSpeed Zulu headset with ANR (active noise reduction). The manufacturer published a service manual for Cessna 210s from 1960-1965. In the service manual, it stated: "Current production 210 models have incorporated a stall and gear warning unit which has two horns built into the unit, thereby eliminating the need of a speaker."