At one point while experimenting with the oscillator, he alleged it generated a resonance in several buildings causing complaints to the police. As the speed grew he said that the machine oscillated at the resonance frequency of his own building and, belatedly realizing the danger, he was forced to use a sledge hammer to terminate the experiment, just as the police arrived.[5] Other versions have Tesla smashing the device before the police arrive and have multi-ton equipment in the basement moving around. Another version has Tesla clamping an oscillator to a building under construction and causing it to vibrate so violently the steelworkers working on it left the building in a panic.[6]