Nor1253 was designed to comply with the class 0 requirement in the international standard for sound calibrators IEC 60942 (1997). The standard is now been replaced by a new version (2003) without this class of performance.
The calibrator is widely used as a replacement for a pistonphone - without the need for correction for the barometric pressure.
Being a class L calibrator (“Laboratory standard” – previous class 0) the Nor1253 is often referred to as the “electronic pistonphone” since it maintains an accuracy normally associated with a pistonphone without the need for a barometer to make corrections for variations in the ambient pressure.