The Extech 407766 is a precision sound level calibrator designed to verify and calibrate sound level meters equipped with 0.5” or 1.0” microphones. It generates a stable 1kHz sine wave at selectable 94dB or 114dB output levels with high accuracy (±0.5dB at 94dB, ±1.0dB at 114dB) and total harmonic distortion (THD) under 2%. Built in a rugged die-cast aluminum housing and compliant with IEC 60942:1997, it features a 3-position switch (OFF/94dB/114dB) and a power-on LED indicator—making it ideal for industrial hygiene, environmental monitoring, and laboratory use.