The sound reference level shall correspond to a recorded short circuit flux of 100 ± 5 nWb/m of track width (r.m.s.) (Federal Republic of Germany: 90 ± 5 nWb/m), at 1 000 Hz. (In some countries,a 400 Hz reference tone is used.) Normal operational practice
ITU-R BR.469-7-2002 history
2002ITU-R BR.469-7-2002 Analogue composite television tape recording Standards for the international exchange of television programmes on magnetic tape***