BRITISH STANDARD BS5550-5.4.3: 1987 ISO162:1985 Cinematography Part5: Common to more than one film gauge Section 5.4 Sound Subsection 5.4.3 Specification for positions and width dimensions of recording and reproducing head gapsfor three-, four- or six-track magnetic sound records on35mm and single-track on17.5mm motion-picture film containing no picture UDC778.534.425:771.531.35