Sound Calibrator Type 4231 is a handy, portable sound source for calibration of sound level meters and other sound measurement equipment. The calibrator is very robust and stable. A leather protecting case, which does not need to be removed to use the calibrator, is supplied. Features Conforms to EN/IEC60942 (2003) Class LS and Class 1, and ANSI S1.40 – 1984 Robust pocket-size design with highly stable level and frequency Calibration accuracy ±0.2 dB 94 dB SPL, or 114 dB SPL for calibration in noisy environments Extremely small influence of static pressure and temperature Sound pressure independent of microphone equivalent volume 1 kHz calibration frequency for correct calibration level independent of weighting networks Fits Brüel &Kjær 1? and 1/2 ?microphones (1/4" and 1/8?microphones with adaptor) Switches off automatically when removed from the microphone