Mayo and others determined the integration and return times by a series of experiments. At first, they intended to create a true peak meter to prevent transmitters from exceeding 100% modulation. They created a prototype meter with an integration time of about 1 ms. They found that the ear tolerates distortion of only a few ms, and that a 'registration time' of 4 ms is sufficient. They made the return time a compromise between a rapid return, which was tiring to the eye—and a slow return, which made control difficult. Engineers decided that the meter should take between 2s and 3s to drop back 26 dB.