Multiplex Sound System of PAL Teletext

Abstract

Three or four companded sound channels accompanying teletext programs can be placed in the back porch of HBL. In this experimental system, a adaptive delta modulation (ADM) scheme with syllable companding is adopted. The audio signal dynamic range level is greater than 45dB and the distortion factor is less than 4 percent. Preliminary experimental results show that an ADM-HBL multiplex sound system is compatible with TV broadcasting and teletext. Its tone quality can satisfy the requirements for additional teletext sound. Because the text signal and sound signal are designed together, the receiver circuits are simplified.